Impair Defenses: Disable Windows Event Logging

Adversaries may disable Windows event logging to limit data that can be leveraged for detections and audits. Windows event logs record user and system activity such as login attempts, process creation, and much more.(Citation: Windows Log Events) This data is used by security tools and analysts to generate detections.

The EventLog service maintains event logs from various system components and applications.(Citation: EventLog_Core_Technologies) By default, the service automatically starts when a system powers on. An audit policy, maintained by the Local Security Policy (secpol.msc), defines which system events the EventLog service logs. Security audit policy settings can be changed by running secpol.msc, then navigating to Security Settings\Local Policies\Audit Policy for basic audit policy settings or Security Settings\Advanced Audit Policy Configuration for advanced audit policy settings.(Citation: Audit_Policy_Microsoft)(Citation: Advanced_sec_audit_policy_settings) auditpol.exe may also be used to set audit policies.(Citation: auditpol)

Adversaries may target system-wide logging or just that of a particular application. For example, the Windows EventLog service may be disabled using the Set-Service -Name EventLog -Status Stopped or sc config eventlog start=disabled commands (followed by manually stopping the service using Stop-Service  -Name EventLog).(Citation: Disable_Win_Event_Logging)(Citation: disable_win_evt_logging) Additionally, the service may be disabled by modifying the “Start” value in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog then restarting the system for the change to take effect.(Citation: disable_win_evt_logging)

There are several ways to disable the EventLog service via registry key modification. First, without Administrator privileges, adversaries may modify the "Start" value in the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-Security, then reboot the system to disable the Security EventLog.(Citation: winser19_file_overwrite_bug_twitter) Second, with Administrator privilege, adversaries may modify the same values in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-System and HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-Application to disable the entire EventLog.(Citation: disable_win_evt_logging)

Additionally, adversaries may use auditpol and its sub-commands in a command prompt to disable auditing or clear the audit policy. To enable or disable a specified setting or audit category, adversaries may use the /success or /failure parameters. For example, auditpol /set /category:”Account Logon” /success:disable /failure:disable turns off auditing for the Account Logon category.(Citation: auditpol.exe_STRONTIC)(Citation: T1562.002_redcanaryco) To clear the audit policy, adversaries may run the following lines: auditpol /clear /y or auditpol /remove /allusers.(Citation: T1562.002_redcanaryco)

By disabling Windows event logging, adversaries can operate while leaving less evidence of a compromise behind.

Monitor processes and command-line arguments for commands that can be used to disable logging. For example, [Wevtutil](https://attack.mitre.org/software/S0645), `auditpol`, `sc stop EventLog`, and offensive tooling (such as [Mimikatz](https://attack.mitre.org/software/S0002) and `Invoke-Phant0m`) may be used to clear logs.(Citation: def_ev_win_event_logging)(Citation: evt_log_tampering)

In Event Viewer, Event ID 1102 under the “Security” Windows Log and Event ID 104 under the “System” Windows Log both indicate logs have been cleared.(Citation: def_ev_win_event_logging) `Service Control Manager Event ID 7035` in Event Viewer may indicate the termination of the EventLog service.(Citation: evt_log_tampering) Additionally, gaps in the logs, e.g. non-sequential Event Record IDs, may indicate that the logs may have been tampered.

Monitor the addition of the MiniNT registry key in `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control`, which may disable Event Viewer.(Citation: def_ev_win_event_logging)


Impair Defenses: Disable or Modify Cloud Firewall

Adversaries may disable or modify a firewall within a cloud environment to bypass controls that limit access to cloud resources. Cloud firewalls are separate from system firewalls that are described in [Disable or Modify System Firewall](https://attack.mitre.org/techniques/T1562/004).

Cloud environments typically utilize restrictive security groups and firewall rules that only allow network activity from trusted IP addresses via expected ports and protocols. An adversary may introduce new firewall rules or policies to allow access into a victim cloud environment. For example, an adversary may use a script or utility that creates new ingress rules in existing security groups to allow any TCP/IP connectivity, or remove networking limitations to support traffic associated with malicious activity (such as cryptomining).(Citation: Expel IO Evil in AWS)(Citation: Palo Alto Unit 42 Compromised Cloud Compute Credentials 2022)

Modifying or disabling a cloud firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed.

Monitor cloud logs for modification or creation of new security groups or firewall rules.


Impair Defenses: Disable or Modify Cloud Logs

An adversary may disable or modify cloud logging capabilities and integrations to limit what data is collected on their activities and avoid detection. Cloud environments allow for collection and analysis of audit and application logs that provide insight into what activities a user does within the environment. If an adversary has sufficient permissions, they can disable or modify logging to avoid detection of their activities.

For example, in AWS an adversary may disable CloudWatch/CloudTrail integrations prior to conducting further malicious activity.(Citation: Following the CloudTrail: Generating strong AWS security signals with Sumo Logic) They may alternatively tamper with logging functionality – for example, by removing any associated SNS topics, disabling multi-region logging, or disabling settings that validate and/or encrypt log files.(Citation: AWS Update Trail)(Citation: Pacu Detection Disruption Module) In Office 365, an adversary may disable logging on mail collection activities for specific users by using the `Set-MailboxAuditBypassAssociation` cmdlet, by disabling M365 Advanced Auditing for the user, or by downgrading the user’s license from an Enterprise E5 to an Enterprise E3 license.(Citation: Dark Reading Microsoft 365 Attacks 2021)

Monitor logs for API calls to disable logging. In AWS, monitor for: StopLogging and DeleteTrail.(Citation: Stopping CloudTrail from Sending Events to CloudWatch Logs) In GCP, monitor for: google.logging.v2.ConfigServiceV2.UpdateSink.(Citation: Configuring Data Access audit logs)  In Azure, monitor for az monitor diagnostic-settings delete.(Citation: az monitor diagnostic-settings) Additionally, a sudden loss of a log source may indicate that it has been disabled.


Impair Defenses: Disable or Modify Linux Audit System

Adversaries may disable or modify the Linux audit system to hide malicious activity and avoid detection. Linux admins use the Linux Audit system to track security-relevant information on a system. The Linux Audit system operates at the kernel-level and maintains event logs on application and system activity such as process, network, file, and login events based on pre-configured rules.

Often referred to as `auditd`, this is the name of the daemon used to write events to disk and is governed by the parameters set in the `audit.conf` configuration file. Two primary ways to configure the log generation rules are through the command line `auditctl` utility and the file `/etc/audit/audit.rules`,  containing a sequence of `auditctl` commands loaded at boot time.(Citation: Red Hat System Auditing)(Citation: IzyKnows auditd threat detection 2022)

With root privileges, adversaries may be able to ensure their activity is not logged through disabling the Audit system service, editing the configuration/rule files, or by hooking the Audit system library functions. Using the command line, adversaries can disable the Audit system service through killing processes associated with `auditd` daemon or use `systemctl` to stop the Audit service. Adversaries can also hook Audit system functions to disable logging or modify the rules contained in the `/etc/audit/audit.rules` or `audit.conf` files to ignore malicious activity.(Citation: Trustwave Honeypot SkidMap 2023)(Citation: ESET Ebury Feb 2014)


Impair Defenses: Disable or Modify System Firewall

Adversaries may disable or modify system firewalls in order to bypass controls limiting network usage. Changes could be disabling the entire mechanism as well as adding, deleting, or modifying particular rules. This can be done numerous ways depending on the operating system, including via command-line, editing Windows Registry keys, and Windows Control Panel.

Modifying or disabling a system firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed. For example, adversaries may add a new firewall rule for a well-known protocol (such as RDP) using a non-traditional and potentially less securitized port (i.e. [Non-Standard Port](https://attack.mitre.org/techniques/T1571)).(Citation: change_rdp_port_conti)

Adversaries may also modify host networking settings that indirectly manipulate system firewalls, such as interface bandwidth or network connection request thresholds.(Citation: Huntress BlackCat) Settings related to enabling abuse of various [Remote Services](https://attack.mitre.org/techniques/T1021) may also indirectly modify firewall rules.

Monitor processes and command-line arguments to see if firewalls are disabled or modified. Monitor Registry edits to keys that manage firewalls.


Impair Defenses: Disable or Modify Tools

Adversaries may modify and/or disable security tools to avoid possible detection of their malware/tools and activities. This may take many forms, such as killing security software processes or services, modifying / deleting Registry keys or configuration files so that tools do not operate properly, or other methods to interfere with security tools scanning or reporting information. Adversaries may also disable updates to prevent the latest security patches from reaching tools on victim systems.(Citation: SCADAfence_ransomware)

Adversaries may also tamper with artifacts deployed and utilized by security tools. Security tools may make dynamic changes to system components in order to maintain visibility into specific events. For example, security products may load their own modules and/or modify those loaded by processes to facilitate data collection. Similar to [Indicator Blocking](https://attack.mitre.org/techniques/T1562/006), adversaries may unhook or otherwise modify these features added by tools (especially those that exist in userland or are otherwise potentially accessible to adversaries) to avoid detection.(Citation: OutFlank System Calls)(Citation: MDSec System Calls)

Adversaries may also focus on specific applications such as Sysmon. For example, the “Start” and “Enable” values in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-Microsoft-Windows-Sysmon-Operational may be modified to tamper with and potentially disable Sysmon logging.(Citation: disable_win_evt_logging)

On network devices, adversaries may attempt to skip digital signature verification checks by altering startup configuration files and effectively disabling firmware verification that typically occurs at boot.(Citation: Fortinet Zero-Day and Custom Malware Used by Suspected Chinese Actor in Espionage Operation)(Citation: Analysis of FG-IR-22-369)

In cloud environments, tools disabled by adversaries may include cloud monitoring agents that report back to services such as AWS CloudWatch or Google Cloud Monitor.

Furthermore, although defensive tools may have anti-tampering mechanisms, adversaries may abuse tools such as legitimate rootkit removal kits to impair and/or disable these tools.(Citation: chasing_avaddon_ransomware)(Citation: dharma_ransomware)(Citation: demystifying_ryuk)(Citation: doppelpaymer_crowdstrike) For example, adversaries have used tools such as GMER to find and shut down hidden processes and antivirus software on infected systems.(Citation: demystifying_ryuk)

Additionally, adversaries may exploit legitimate drivers from anti-virus software to gain access to kernel space (i.e. [Exploitation for Privilege Escalation](https://attack.mitre.org/techniques/T1068)), which may lead to bypassing anti-tampering features.(Citation: avoslocker_ransomware)

Monitor processes and command-line arguments to see if security tools/services are killed or stop running. Monitor Registry edits for modifications to services and startup programs that correspond to security tools. Monitoring for changes to other known features used by deployed security tools may also expose malicious activity.

Lack of expected log events may be suspicious.


Impair Defenses: Downgrade Attack

Adversaries may downgrade or use a version of system features that may be outdated, vulnerable, and/or does not support updated security controls. Downgrade attacks typically take advantage of a system’s backward compatibility to force it into less secure modes of operation.

Adversaries may downgrade and use various less-secure versions of features of a system, such as [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059)s or even network protocols that can be abused to enable [Adversary-in-the-Middle](https://attack.mitre.org/techniques/T1557) or [Network Sniffing](https://attack.mitre.org/techniques/T1040).(Citation: Praetorian TLS Downgrade Attack 2014) For example, [PowerShell](https://attack.mitre.org/techniques/T1059/001) versions 5+ includes Script Block Logging (SBL) which can record executed script content. However, adversaries may attempt to execute a previous version of PowerShell that does not support SBL with the intent to [Impair Defenses](https://attack.mitre.org/techniques/T1562) while running malicious scripts that may have otherwise been detected.(Citation: CrowdStrike BGH Ransomware 2021)(Citation: Mandiant BYOL 2018)(Citation: att_def_ps_logging)

Adversaries may similarly target network traffic to downgrade from an encrypted HTTPS connection to an unsecured HTTP connection that exposes network data in clear text.(Citation: Targeted SSL Stripping Attacks Are Real)(Citation: Crowdstrike Downgrade)

Monitor for commands or other activity that may be indicative of attempts to abuse older or deprecated technologies (ex: powershell –v 2). Also monitor for other abnormal events, such as execution of and/or processes spawning from a version of a tool that is not expected in the environment.

Monitor for Windows event ID (EID) 400, specifically the EngineVersion field which shows the version of PowerShell running and may highlight a malicious downgrade attack.(Citation: inv_ps_attacks)

Monitor network data to detect cases where HTTP is used instead of HTTPS.


Impair Defenses: Impair Command History Logging

Adversaries may impair command history logging to hide commands they run on a compromised system. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they've done.

On Linux and macOS, command history is tracked in a file pointed to by the environment variable HISTFILE. When a user logs off a system, this information is flushed to a file in the user's home directory called ~/.bash_history. The HISTCONTROL environment variable keeps track of what should be saved by the history command and eventually into the ~/.bash_history file when a user logs out. HISTCONTROL does not exist by default on macOS, but can be set by the user and will be respected.

Adversaries may clear the history environment variable (unset HISTFILE) or set the command history size to zero (export HISTFILESIZE=0) to prevent logging of commands. Additionally, HISTCONTROL can be configured to ignore commands that start with a space by simply setting it to "ignorespace". HISTCONTROL can also be set to ignore duplicate commands by setting it to "ignoredups". In some Linux systems, this is set by default to "ignoreboth" which covers both of the previous examples. This means that “ ls” will not be saved, but “ls” would be saved by history. Adversaries can abuse this to operate without leaving traces by simply prepending a space to all of their terminal commands.

On Windows systems, the PSReadLine module tracks commands used in all PowerShell sessions and writes them to a file ($env:APPDATA\Microsoft\Windows\PowerShell\PSReadLine\ConsoleHost_history.txt by default). Adversaries may change where these logs are saved using Set-PSReadLineOption -HistorySavePath {File Path}. This will cause ConsoleHost_history.txt to stop receiving logs. Additionally, it is possible to turn off logging to this file using the PowerShell command Set-PSReadlineOption -HistorySaveStyle SaveNothing.(Citation: Microsoft PowerShell Command History)(Citation: Sophos PowerShell command audit)(Citation: Sophos PowerShell Command History Forensics)

Adversaries may also leverage a [Network Device CLI](https://attack.mitre.org/techniques/T1059/008) on network devices to disable historical command logging (e.g. no logging).

Correlating a user session with a distinct lack of new commands in their .bash_history can be a clue to suspicious behavior. Additionally, users checking or changing their HISTCONTROL, HISTFILE, or HISTFILESIZE environment variables may be suspicious.

Monitor for modification of PowerShell command history settings through processes being created with -HistorySaveStyle SaveNothing command-line arguments and use of the PowerShell commands Set-PSReadlineOption -HistorySaveStyle SaveNothing and Set-PSReadLineOption -HistorySavePath {File Path}. Further, [Network Device CLI](https://attack.mitre.org/techniques/T1059/008) commands may also be used to clear or disable historical log data with built-in features native to the network device platform.  Monitor such command activity for unexpected or unauthorized use of commands being run by non-standard users from non-standard locations.


Impair Defenses: Indicator Blocking

An adversary may attempt to block indicators or events typically captured by sensors from being gathered and analyzed. This could include maliciously redirecting(Citation: Microsoft Lamin Sept 2017) or even disabling host-based sensors, such as Event Tracing for Windows (ETW)(Citation: Microsoft About Event Tracing 2018), by tampering settings that control the collection and flow of event telemetry.(Citation: Medium Event Tracing Tampering 2018) These settings may be stored on the system in configuration files and/or in the Registry as well as being accessible via administrative utilities such as [PowerShell](https://attack.mitre.org/techniques/T1059/001) or [Windows Management Instrumentation](https://attack.mitre.org/techniques/T1047).

For example, adversaries may modify the `File` value in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\Security to hide their malicious actions in a new or different .evtx log file. This action does not require a system reboot and takes effect immediately.(Citation: disable_win_evt_logging)

ETW interruption can be achieved multiple ways, however most directly by defining conditions using the [PowerShell](https://attack.mitre.org/techniques/T1059/001) Set-EtwTraceProvider cmdlet or by interfacing directly with the Registry to make alterations.

In the case of network-based reporting of indicators, an adversary may block traffic associated with reporting to prevent central analysis. This may be accomplished by many means, such as stopping a local process responsible for forwarding telemetry and/or creating a host-based firewall rule to block traffic to specific hosts responsible for aggregating events, such as security information and event management (SIEM) products.

In Linux environments, adversaries may disable or reconfigure log processing tools such as syslog or nxlog to inhibit detection and monitoring capabilities to facilitate follow on behaviors (Citation: LemonDuck).

Detect lack of reported activity from a host sensor. Different methods of blocking may cause different disruptions in reporting. Systems may suddenly stop reporting all data or only certain kinds of data.

Depending on the types of host information collected, an analyst may be able to detect the event that triggered a process to stop or connection to be blocked. For example, Sysmon will log when its configuration state has changed (Event ID 16) and Windows Management Instrumentation (WMI) may be used to subscribe ETW providers that log any provider removal from a specific trace session. (Citation: Medium Event Tracing Tampering 2018) To detect changes in ETW you can also monitor the registry key which contains configurations for all ETW event providers: HKLM\SYSTEM\CurrentControlSet\Control\WMI\Autologger\AUTOLOGGER_NAME\{PROVIDER_GUID}


Impair Defenses: Safe Mode Boot

Adversaries may abuse Windows safe mode to disable endpoint defenses. Safe mode starts up the Windows operating system with a limited set of drivers and services. Third-party security software such as endpoint detection and response (EDR) tools may not start after booting Windows in safe mode. There are two versions of safe mode: Safe Mode and Safe Mode with Networking. It is possible to start additional services after a safe mode boot.(Citation: Microsoft Safe Mode)(Citation: Sophos Snatch Ransomware 2019)

Adversaries may abuse safe mode to disable endpoint defenses that may not start with a limited boot. Hosts can be forced into safe mode after the next reboot via modifications to Boot Configuration Data (BCD) stores, which are files that manage boot application settings.(Citation: Microsoft bcdedit 2021)

Adversaries may also add their malicious applications to the list of minimal services that start in safe mode by modifying relevant Registry values (i.e. [Modify Registry](https://attack.mitre.org/techniques/T1112)). Malicious [Component Object Model](https://attack.mitre.org/techniques/T1559/001) (COM) objects may also be registered and loaded in safe mode.(Citation: Sophos Snatch Ransomware 2019)(Citation: CyberArk Labs Safe Mode 2016)(Citation: Cybereason Nocturnus MedusaLocker 2020)(Citation: BleepingComputer REvil 2021)

Monitor Registry modification and additions for services that may start on safe mode. For example, a program can be forced to start on safe mode boot by adding a \* in front of the "Startup" value name: HKLM\Software\Microsoft\Windows\CurrentVersion\Run\["\*Startup"="{Path}"] or by adding a key to HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal.(Citation: BleepingComputer REvil 2021)(Citation: Sophos Snatch Ransomware 2019)

Monitor execution of processes and commands associated with making configuration changes to boot settings, such as bcdedit.exe and bootcfg.exe.(Citation: Microsoft bcdedit 2021)(Citation: Microsoft Bootcfg)(Citation: Sophos Snatch Ransomware 2019)


Impair Defenses: Spoof Security Alerting

Adversaries may spoof security alerting from tools, presenting false evidence to impair defenders’ awareness of malicious activity.(Citation: BlackBasta) Messages produced by defensive tools contain information about potential security events as well as the functioning status of security software and the system. Security reporting messages are important for monitoring the normal operation of a system and identifying important events that can signal a security incident.

Rather than or in addition to [Indicator Blocking](https://attack.mitre.org/techniques/T1562/006), an adversary can spoof positive affirmations that security tools are continuing to function even after legitimate security tools have been disabled (e.g., [Disable or Modify Tools](https://attack.mitre.org/techniques/T1562/001)). An adversary can also present a “healthy” system status even after infection. This can be abused to enable further malicious activity by delaying defender responses.

For example, adversaries may show a fake Windows Security GUI and tray icon with a “healthy” system status after Windows Defender and other system tools have been disabled.(Citation: BlackBasta)


Impersonation

Adversaries may impersonate a trusted person or organization in order to persuade and trick a target into performing some action on their behalf. For example, adversaries may communicate with victims (via [Phishing for Information](https://attack.mitre.org/techniques/T1598), [Phishing](https://attack.mitre.org/techniques/T1566), or [Internal Spearphishing](https://attack.mitre.org/techniques/T1534)) while impersonating a known sender such as an executive, colleague, or third-party vendor. Established trust can then be leveraged to accomplish an adversary’s ultimate goals, possibly against multiple victims.

In many cases of business email compromise or email fraud campaigns, adversaries use impersonation to defraud victims -- deceiving them into sending money or divulging information that ultimately enables [Financial Theft](https://attack.mitre.org/techniques/T1657).

Adversaries will often also use social engineering techniques such as manipulative and persuasive language in email subject lines and body text such as `payment`, `request`, or `urgent` to push the victim to act quickly before malicious activity is detected. These campaigns are often specifically targeted against people who, due to job roles and/or accesses, can carry out the adversary’s goal.

Impersonation is typically preceded by reconnaissance techniques such as [Gather Victim Identity Information](https://attack.mitre.org/techniques/T1589) and [Gather Victim Org Information](https://attack.mitre.org/techniques/T1591) as well as acquiring infrastructure such as email domains (i.e. [Domains](https://attack.mitre.org/techniques/T1583/001)) to substantiate their false identity.(Citation: CrowdStrike-BEC)

There is the potential for multiple victims in campaigns involving impersonation. For example, an adversary may [Compromise Accounts](https://attack.mitre.org/techniques/T1586) targeting one organization which can then be used to support impersonation against other entities.(Citation: VEC)


Implant Internal Image

Adversaries may implant cloud or container images with malicious code to establish persistence after gaining access to an environment. Amazon Web Services (AWS) Amazon Machine Images (AMIs), Google Cloud Platform (GCP) Images, and Azure Images as well as popular container runtimes such as Docker can be implanted or backdoored. Unlike [Upload Malware](https://attack.mitre.org/techniques/T1608/001), this technique focuses on adversaries implanting an image in a registry within a victim’s environment. Depending on how the infrastructure is provisioned, this could provide persistent access if the infrastructure provisioning tool is instructed to always use the latest image.(Citation: Rhino Labs Cloud Image Backdoor Technique Sept 2019)

A tool has been developed to facilitate planting backdoors in cloud container images.(Citation: Rhino Labs Cloud Backdoor September 2019) If an adversary has access to a compromised AWS instance, and permissions to list the available container images, they may implant a backdoor such as a [Web Shell](https://attack.mitre.org/techniques/T1505/003).(Citation: Rhino Labs Cloud Image Backdoor Technique Sept 2019)

Monitor interactions with images and containers by users to identify ones that are added or modified anomalously.

In containerized environments, changes may be detectable by monitoring the Docker daemon logs or setting up and monitoring Kubernetes audit logs depending on registry configuration.


Indicator Removal

Adversaries may delete or modify artifacts generated within systems to remove evidence of their presence or hinder defenses. Various artifacts may be created by an adversary or something that can be attributed to an adversary’s actions. Typically these artifacts are used as defensive indicators related to monitored events, such as strings from downloaded files, logs that are generated from user actions, and other data analyzed by defenders. Location, format, and type of artifact (such as command or login history) are often specific to each platform.

Removal of these indicators may interfere with event collection, reporting, or other processes used to detect intrusion activity. This may compromise the integrity of security solutions by causing notable events to go unreported. This activity may also impede forensic analysis and incident response, due to lack of sufficient data to determine what occurred.

File system monitoring may be used to detect improper deletion or modification of indicator files.  Events not stored on the file system may require different detection mechanisms.


Indicator Removal: Clear Command History

In addition to clearing system logs, an adversary may clear the command history of a compromised account to conceal the actions undertaken during an intrusion. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they've done.

On Linux and macOS, these command histories can be accessed in a few different ways. While logged in, this command history is tracked in a file pointed to by the environment variable HISTFILE. When a user logs off a system, this information is flushed to a file in the user's home directory called ~/.bash_history. The benefit of this is that it allows users to go back to commands they've used before in different sessions.

Adversaries may delete their commands from these logs by manually clearing the history (history -c) or deleting the bash history file rm ~/.bash_history.

Adversaries may also leverage a [Network Device CLI](https://attack.mitre.org/techniques/T1059/008) on network devices to clear command history data (clear logging and/or clear history).(Citation: US-CERT-TA18-106A)

On Windows hosts, PowerShell has two different command history providers: the built-in history and the command history managed by the PSReadLine module. The built-in history only tracks the commands used in the current session. This command history is not available to other sessions and is deleted when the session ends.

The PSReadLine command history tracks the commands used in all PowerShell sessions and writes them to a file ($env:APPDATA\Microsoft\Windows\PowerShell\PSReadLine\ConsoleHost_history.txt by default). This history file is available to all sessions and contains all past history since the file is not deleted when the session ends.(Citation: Microsoft PowerShell Command History)

Adversaries may run the PowerShell command Clear-History to flush the entire command history from a current PowerShell session. This, however, will not delete/flush the ConsoleHost_history.txt file. Adversaries may also delete the ConsoleHost_history.txt file or edit its contents to hide PowerShell commands they have run.(Citation: Sophos PowerShell command audit)(Citation: Sophos PowerShell Command History Forensics)

User authentication, especially via remote terminal services like SSH, without new entries in that user's ~/.bash_history is suspicious. Additionally, the removal/clearing of the ~/.bash_history file can be an indicator of suspicious activity.

Monitor for suspicious modifications or deletion of ConsoleHost_history.txt and use of the Clear-History command.


Indicator Removal: Clear Linux or Mac System Logs

Adversaries may clear system logs to hide evidence of an intrusion. macOS and Linux both keep track of system or user-initiated actions via system logs. The majority of native system logging is stored under the /var/log/ directory. Subfolders in this directory categorize logs by their related functions, such as:(Citation: Linux Logs)

* /var/log/messages:: General and system-related messages
* /var/log/secure or /var/log/auth.log: Authentication logs
* /var/log/utmp or /var/log/wtmp: Login records
* /var/log/kern.log: Kernel logs
* /var/log/cron.log: Crond logs
* /var/log/maillog: Mail server logs
* /var/log/httpd/: Web server access and error logs

File system monitoring may be used to detect improper deletion or modification of indicator files. Also monitor for suspicious processes interacting with log files.


Indicator Removal: Clear Mailbox Data

Adversaries may modify mail and mail application data to remove evidence of their activity. Email applications allow users and other programs to export and delete mailbox data via command line tools or use of APIs. Mail application data can be emails, email metadata, or logs generated by the application or operating system, such as export requests.

Adversaries may manipulate emails and mailbox data to remove logs, artifacts, and metadata, such as evidence of [Phishing](https://attack.mitre.org/techniques/T1566)/[Internal Spearphishing](https://attack.mitre.org/techniques/T1534), [Email Collection](https://attack.mitre.org/techniques/T1114), [Mail Protocols](https://attack.mitre.org/techniques/T1071/003) for command and control, or email-based exfiltration such as [Exfiltration Over Alternative Protocol](https://attack.mitre.org/techniques/T1048). For example, to remove evidence on Exchange servers adversaries have used the ExchangePowerShell [PowerShell](https://attack.mitre.org/techniques/T1059/001) module, including Remove-MailboxExportRequest to remove evidence of mailbox exports.(Citation: Volexity SolarWinds)(Citation: ExchangePowerShell Module) On Linux and macOS, adversaries may also delete emails through a command line utility called mail  or use [AppleScript](https://attack.mitre.org/techniques/T1059/002) to interact with APIs on macOS.(Citation: Cybereason Cobalt Kitty 2017)(Citation: mailx man page)

Adversaries may also remove emails and metadata/headers indicative of spam or suspicious activity (for example, through the use of organization-wide transport rules) to reduce the likelihood of malicious emails being detected by security products.(Citation: Microsoft OAuth Spam 2022)


Indicator Removal: Clear Network Connection History and Configurations

Adversaries may clear or remove evidence of malicious network connections in order to clean up traces of their operations. Configuration settings as well as various artifacts that highlight connection history may be created on a system and/or in application logs from behaviors that require network connections, such as [Remote Services](https://attack.mitre.org/techniques/T1021) or [External Remote Services](https://attack.mitre.org/techniques/T1133). Defenders may use these artifacts to monitor or otherwise analyze network connections created by adversaries.

Network connection history may be stored in various locations. For example, RDP connection history may be stored in Windows Registry values under (Citation: Microsoft RDP Removal):

* HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Default
* HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Servers

Windows may also store information about recent RDP connections in files such as C:\Users\\%username%\Documents\Default.rdp and `C:\Users\%username%\AppData\Local\Microsoft\Terminal
Server Client\Cache\`.(Citation: Moran RDPieces) Similarly, macOS and Linux hosts may store information highlighting connection history in system logs (such as those stored in `/Library/Logs` and/or `/var/log/`).(Citation: Apple Culprit Access)(Citation: FreeDesktop Journal)(Citation: Apple Unified Log Analysis Remote Login and Screen Sharing)

Malicious network connections may also require changes to third-party applications or network configuration settings, such as [Disable or Modify System Firewall](https://attack.mitre.org/techniques/T1562/004) or tampering to enable [Proxy](https://attack.mitre.org/techniques/T1090). Adversaries may delete or modify this data to conceal indicators and/or impede defensive analysis.


Indicator Removal: Clear Persistence

Adversaries may clear artifacts associated with previously established persistence on a host system to remove evidence of their activity. This may involve various actions, such as removing services, deleting executables, [Modify Registry](https://attack.mitre.org/techniques/T1112), [Plist File Modification](https://attack.mitre.org/techniques/T1647), or other methods of cleanup to prevent defenders from collecting evidence of their persistent presence.(Citation: Cylance Dust Storm) Adversaries may also delete accounts previously created to maintain persistence (i.e. [Create Account](https://attack.mitre.org/techniques/T1136)).(Citation: Talos - Cisco Attack 2022)

In some instances, artifacts of persistence may also be removed once an adversary’s persistence is executed in order to prevent errors with the new instance of the malware.(Citation: NCC Group Team9 June 2020)


Indicator Removal: Clear Windows Event Logs

Adversaries may clear Windows Event Logs to hide the activity of an intrusion. Windows Event Logs are a record of a computer's alerts and notifications. There are three system-defined sources of events: System, Application, and Security, with five event types: Error, Warning, Information, Success Audit, and Failure Audit.

With administrator privileges, the event logs can be cleared with the following utility commands:

* wevtutil cl system
* wevtutil cl application
* wevtutil cl security

These logs may also be cleared through other mechanisms, such as the event viewer GUI or [PowerShell](https://attack.mitre.org/techniques/T1059/001). For example, adversaries may use the PowerShell command Remove-EventLog -LogName Security to delete the Security EventLog and after reboot, disable future logging.  Note: events may still be generated and logged in the .evtx file between the time the command is run and the reboot.(Citation: disable_win_evt_logging)

Adversaries may also attempt to clear logs by directly deleting the stored log files within `C:\Windows\System32\winevt\logs\`.

Deleting Windows event logs (via native binaries (Citation: Microsoft wevtutil Oct 2017), API functions (Citation: Microsoft EventLog.Clear), or [PowerShell](https://attack.mitre.org/techniques/T1059/001) (Citation: Microsoft Clear-EventLog)) may also generate an alterable event (Event ID 1102: "The audit log was cleared").


Indicator Removal: File Deletion

Adversaries may delete files left behind by the actions of their intrusion activity. Malware, tools, or other non-native files dropped or created on a system by an adversary (ex: [Ingress Tool Transfer](https://attack.mitre.org/techniques/T1105)) may leave traces to indicate to what was done within a network and how. Removal of these files can occur during an intrusion, or as part of a post-intrusion process to minimize the adversary's footprint.

There are tools available from the host operating system to perform cleanup, but adversaries may use other tools as well.(Citation: Microsoft SDelete July 2016) Examples of built-in [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059) functions include del on Windows and rm or unlink on Linux and macOS.

It may be uncommon for events related to benign command-line functions such as DEL or third-party utilities or tools to be found in an environment, depending on the user base and how systems are typically used. Monitoring for command-line deletion functions to correlate with binaries or other files that an adversary may drop and remove may lead to detection of malicious activity. Another good practice is monitoring for known deletion and secure deletion tools that are not already on systems within an enterprise network that an adversary could introduce. Some monitoring tools may collect command-line arguments, but may not capture DEL commands since DEL is a native function within cmd.exe.


Indicator Removal: Network Share Connection Removal

Adversaries may remove share connections that are no longer useful in order to clean up traces of their operation. Windows shared drive and [SMB/Windows Admin Shares](https://attack.mitre.org/techniques/T1021/002) connections can be removed when no longer needed. [Net](https://attack.mitre.org/software/S0039) is an example utility that can be used to remove network share connections with the net use \\system\share /delete command. (Citation: Technet Net Use)

Network share connections may be common depending on how an network environment is used. Monitor command-line invocation of net use commands associated with establishing and removing remote shares over SMB, including following best practices for detection of [Windows Admin Shares](https://attack.mitre.org/techniques/T1077). SMB traffic between systems may also be captured and decoded to look for related network share session and file transfer activity. Windows authentication logs are also useful in determining when authenticated network shares are established and by which account, and can be used to correlate network share activity to other events to investigate potentially malicious activity.


Indicator Removal: Timestomp

Adversaries may modify file time attributes to hide new or changes to existing files. Timestomping is a technique that modifies the timestamps of a file (the modify, access, create, and change times), often to mimic files that are in the same folder. This is done, for example, on files that have been modified or created by the adversary so that they do not appear conspicuous to forensic investigators or file analysis tools.

Timestomping may be used along with file name [Masquerading](https://attack.mitre.org/techniques/T1036) to hide malware and tools.(Citation: WindowsIR Anti-Forensic Techniques)

Forensic techniques exist to detect aspects of files that have had their timestamps modified. (Citation: WindowsIR Anti-Forensic Techniques) It may be possible to detect timestomping using file modification monitoring that collects information on file handle opens and can compare timestamp values.


Indirect Command Execution

Adversaries may abuse utilities that allow for command execution to bypass security restrictions that limit the use of command-line interpreters. Various Windows utilities may be used to execute commands, possibly without invoking [cmd](https://attack.mitre.org/software/S0106). For example, [Forfiles](https://attack.mitre.org/software/S0193), the Program Compatibility Assistant (pcalua.exe), components of the Windows Subsystem for Linux (WSL), as well as other utilities may invoke the execution of programs and commands from a [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059), Run window, or via scripts. (Citation: VectorSec ForFiles Aug 2017) (Citation: Evi1cg Forfiles Nov 2017)

Adversaries may abuse these features for [Defense Evasion](https://attack.mitre.org/tactics/TA0005), specifically to perform arbitrary execution while subverting detections and/or mitigation controls (such as Group Policy) that limit/prevent the usage of [cmd](https://attack.mitre.org/software/S0106) or file extensions more commonly associated with malicious payloads.

Monitor and analyze logs from host-based detection mechanisms, such as Sysmon, for events such as process creations that include or are resulting from parameters associated with invoking programs/commands/files and/or spawning child processes/network connections. (Citation: RSA Forfiles Aug 2017)


Ingress Tool Transfer

Adversaries may transfer tools or other files from an external system into a compromised environment. Tools or files may be copied from an external adversary-controlled system to the victim network through the command and control channel or through alternate protocols such as [ftp](https://attack.mitre.org/software/S0095). Once present, adversaries may also transfer/spread tools between victim devices within a compromised environment (i.e. [Lateral Tool Transfer](https://attack.mitre.org/techniques/T1570)).

On Windows, adversaries may use various utilities to download tools, such as `copy`, `finger`, [certutil](https://attack.mitre.org/software/S0160), and [PowerShell](https://attack.mitre.org/techniques/T1059/001) commands such as IEX(New-Object Net.WebClient).downloadString() and Invoke-WebRequest. On Linux and macOS systems, a variety of utilities also exist, such as `curl`, `scp`, `sftp`, `tftp`, `rsync`, `finger`, and `wget`.(Citation: t1105_lolbas)

Adversaries may also abuse installers and package managers, such as `yum` or `winget`, to download tools to victim hosts. Adversaries have also abused file application features, such as the Windows `search-ms` protocol handler, to deliver malicious files to victims through remote file searches invoked by [User Execution](https://attack.mitre.org/techniques/T1204) (typically after interacting with [Phishing](https://attack.mitre.org/techniques/T1566) lures).(Citation: T1105: Trellix_search-ms)

Files can also be transferred using various [Web Service](https://attack.mitre.org/techniques/T1102)s as well as native or otherwise present tools on the victim system.(Citation: PTSecurity Cobalt Dec 2016) In some cases, adversaries may be able to leverage services that sync between a web-based and an on-premises client, such as Dropbox or OneDrive, to transfer files onto victim systems. For example, by compromising a cloud account and logging into the service's web portal, an adversary may be able to trigger an automatic syncing process that transfers the file onto the victim's machine.(Citation: Dropbox Malware Sync)

Monitor for file creation and files transferred into the network. Unusual processes with external network connections creating files on-system may be suspicious. Use of utilities, such as [ftp](https://attack.mitre.org/software/S0095), that does not normally occur may also be suspicious.

Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Specifically, for the finger utility on Windows and Linux systems, monitor command line or terminal execution for the finger command. Monitor network activity for TCP port 79, which is used by the finger utility, and Windows netsh interface portproxy modifications to well-known ports such as 80 and 443. Furthermore, monitor file system for the download/creation and execution of suspicious files, which may indicate adversary-downloaded payloads. Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used.(Citation: University of Birmingham C2)


Inhibit System Recovery

Adversaries may delete or remove built-in data and turn off services designed to aid in the recovery of a corrupted system to prevent recovery.(Citation: Talos Olympic Destroyer 2018)(Citation: FireEye WannaCry 2017) This may deny access to available backups and recovery options.

Operating systems may contain features that can help fix corrupted systems, such as a backup catalog, volume shadow copies, and automatic repair features. Adversaries may disable or delete system recovery features to augment the effects of [Data Destruction](https://attack.mitre.org/techniques/T1485) and [Data Encrypted for Impact](https://attack.mitre.org/techniques/T1486).(Citation: Talos Olympic Destroyer 2018)(Citation: FireEye WannaCry 2017) Furthermore, adversaries may disable recovery notifications, then corrupt backups.(Citation: disable_notif_synology_ransom)

A number of native Windows utilities have been used by adversaries to disable or delete system recovery features:

* vssadmin.exe can be used to delete all volume shadow copies on a system - vssadmin.exe delete shadows /all /quiet
* [Windows Management Instrumentation](https://attack.mitre.org/techniques/T1047) can be used to delete volume shadow copies - wmic shadowcopy delete
* wbadmin.exe can be used to delete the Windows Backup Catalog - wbadmin.exe delete catalog -quiet
* bcdedit.exe can be used to disable automatic Windows recovery features by modifying boot configuration data - bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures & bcdedit /set {default} recoveryenabled no
* REAgentC.exe can be used to disable Windows Recovery Environment (WinRE) repair/recovery options of an infected system
* diskshadow.exe can be used to delete all volume shadow copies on a system - diskshadow delete shadows all (Citation: Diskshadow) (Citation: Crytox Ransomware)

On network devices, adversaries may leverage [Disk Wipe](https://attack.mitre.org/techniques/T1561) to delete backup firmware images and reformat the file system, then [System Shutdown/Reboot](https://attack.mitre.org/techniques/T1529) to reload the device. Together this activity may leave network devices completely inoperable and inhibit recovery operations.

Adversaries may also delete “online” backups that are connected to their network – whether via network storage media or through folders that sync to cloud services.(Citation: ZDNet Ransomware Backups 2020) In cloud environments, adversaries may disable versioning and backup policies and delete snapshots, machine images, and prior versions of objects designed to be used in disaster recovery scenarios.(Citation: Dark Reading Code Spaces Cyber Attack)(Citation: Rhino Security Labs AWS S3 Ransomware)

Use process monitoring to monitor the execution and command line parameters of binaries involved in inhibiting system recovery, such as vssadmin, wbadmin, bcdedit, REAgentC, and diskshadow. The Windows event logs, ex. Event ID 524 indicating a system catalog was deleted, may contain entries associated with suspicious activity.

Monitor the status of services involved in system recovery. Monitor the registry for changes associated with system recovery features (ex: the creation of HKEY_CURRENT_USER\Software\Policies\Microsoft\PreviousVersions\DisableLocalPage).

For network infrastructure devices, collect AAA logging to monitor for `erase`, `format`, and `reload` commands being run in succession.


Input Capture

Adversaries may use methods of capturing user input to obtain credentials or collect information. During normal system usage, users often provide credentials to various different locations, such as login pages/portals or system dialog boxes. Input capture mechanisms may be transparent to the user (e.g. [Credential API Hooking](https://attack.mitre.org/techniques/T1056/004)) or rely on deceiving the user into providing input into what they believe to be a genuine service (e.g. [Web Portal Capture](https://attack.mitre.org/techniques/T1056/003)).

Detection may vary depending on how input is captured but may include monitoring for certain Windows API calls (e.g. `SetWindowsHook`, `GetKeyState`, and `GetAsyncKeyState`)(Citation: Adventures of a Keystroke), monitoring for malicious instances of [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059), and ensuring no unauthorized drivers or kernel modules that could indicate keylogging or API hooking are present.


Input Capture: Credential API Hooking

Adversaries may hook into Windows application programming interface (API) functions to collect user credentials. Malicious hooking mechanisms may capture API calls that include parameters that reveal user authentication credentials.(Citation: Microsoft TrojanSpy:Win32/Ursnif.gen!I Sept 2017) Unlike [Keylogging](https://attack.mitre.org/techniques/T1056/001),  this technique focuses specifically on API functions that include parameters that reveal user credentials. Hooking involves redirecting calls to these functions and can be implemented via:

* **Hooks procedures**, which intercept and execute designated code in response to events such as messages, keystrokes, and mouse inputs.(Citation: Microsoft Hook Overview)(Citation: Elastic Process Injection July 2017)
* **Import address table (IAT) hooking**, which use modifications to a process’s IAT, where pointers to imported API functions are stored.(Citation: Elastic Process Injection July 2017)(Citation: Adlice Software IAT Hooks Oct 2014)(Citation: MWRInfoSecurity Dynamic Hooking 2015)
* **Inline hooking**, which overwrites the first bytes in an API function to redirect code flow.(Citation: Elastic Process Injection July 2017)(Citation: HighTech Bridge Inline Hooking Sept 2011)(Citation: MWRInfoSecurity Dynamic Hooking 2015)

Monitor for calls to the `SetWindowsHookEx` and `SetWinEventHook` functions, which install a hook procedure.(Citation: Microsoft Hook Overview)(Citation: Volatility Detecting Hooks Sept 2012) Also consider analyzing hook chains (which hold pointers to hook procedures for each type of hook) using tools(Citation: Volatility Detecting Hooks Sept 2012)(Citation: PreKageo Winhook Jul 2011)(Citation: Jay GetHooks Sept 2011) or by programmatically examining internal kernel structures.(Citation: Zairon Hooking Dec 2006)(Citation: EyeofRa Detecting Hooking June 2017)

Rootkits detectors(Citation: GMER Rootkits) can also be used to monitor for various types of hooking activity.

Verify integrity of live processes by comparing code in memory to that of corresponding static binaries, specifically checking for jumps and other instructions that redirect code flow. Also consider taking snapshots of newly started processes(Citation: Microsoft Process Snapshot) to compare the in-memory IAT to the real addresses of the referenced functions.(Citation: StackExchange Hooks Jul 2012)(Citation: Adlice Software IAT Hooks Oct 2014)


Input Capture: GUI Input Capture

Adversaries may mimic common operating system GUI components to prompt users for credentials with a seemingly legitimate prompt. When programs are executed that need additional privileges than are present in the current user context, it is common for the operating system to prompt the user for proper credentials to authorize the elevated privileges for the task (ex: [Bypass User Account Control](https://attack.mitre.org/techniques/T1548/002)).

Adversaries may mimic this functionality to prompt users for credentials with a seemingly legitimate prompt for a number of reasons that mimic normal usage, such as a fake installer requiring additional access or a fake malware removal suite.(Citation: OSX Malware Exploits MacKeeper) This type of prompt can be used to collect credentials via various languages such as [AppleScript](https://attack.mitre.org/techniques/T1059/002)(Citation: LogRhythm Do You Trust Oct 2014)(Citation: OSX Keydnap malware)(Citation: Spoofing credential dialogs) and [PowerShell](https://attack.mitre.org/techniques/T1059/001).(Citation: LogRhythm Do You Trust Oct 2014)(Citation: Enigma Phishing for Credentials Jan 2015)(Citation: Spoofing credential dialogs) On Linux systems adversaries may launch dialog boxes prompting users for credentials from malicious shell scripts or the command line (i.e. [Unix Shell](https://attack.mitre.org/techniques/T1059/004)).(Citation: Spoofing credential dialogs)

Adversaries may also mimic common software authentication requests, such as those from browsers or email clients. This may also be paired with user activity monitoring (i.e., [Browser Information Discovery](https://attack.mitre.org/techniques/T1217) and/or [Application Window Discovery](https://attack.mitre.org/techniques/T1010)) to spoof prompts when users are naturally accessing sensitive sites/data.

Monitor process execution for unusual programs as well as malicious instances of [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059) that could be used to prompt users for credentials. For example, command/script history including abnormal parameters (such as requests for credentials and/or strings related to creating password prompts) may be malicious.(Citation: Spoofing credential dialogs)

Inspect and scrutinize input prompts for indicators of illegitimacy, such as non-traditional banners, text, timing, and/or sources.


Input Capture: Keylogging

Adversaries may log user keystrokes to intercept credentials as the user types them. Keylogging is likely to be used to acquire credentials for new access opportunities when [OS Credential Dumping](https://attack.mitre.org/techniques/T1003) efforts are not effective, and may require an adversary to intercept keystrokes on a system for a substantial period of time before credentials can be successfully captured. In order to increase the likelihood of capturing credentials quickly, an adversary may also perform actions such as clearing browser cookies to force users to reauthenticate to systems.(Citation: Talos Kimsuky Nov 2021)

Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes.(Citation: Adventures of a Keystroke) Some methods include:

* Hooking API callbacks used for processing keystrokes. Unlike [Credential API Hooking](https://attack.mitre.org/techniques/T1056/004), this focuses solely on API functions intended for processing keystroke data.
* Reading raw keystroke data from the hardware buffer.
* Windows Registry modifications.
* Custom drivers.
* [Modify System Image](https://attack.mitre.org/techniques/T1601) may provide adversaries with hooks into the operating system of network devices to read raw keystrokes for login sessions.(Citation: Cisco Blog Legacy Device Attacks)

Keyloggers may take many forms, possibly involving modification to the Registry and installation of a driver, setting a hook, or polling to intercept keystrokes. Commonly used API calls include `SetWindowsHook`, `GetKeyState`, and `GetAsyncKeyState`.(Citation: Adventures of a Keystroke) Monitor the Registry and file system for such changes, monitor driver installs, and look for common keylogging API calls. API calls alone are not an indicator of keylogging, but may provide behavioral data that is useful when combined with other information such as new files written to disk and unusual processes.


Input Capture: Web Portal Capture

Adversaries may install code on externally facing portals, such as a VPN login page, to capture and transmit credentials of users who attempt to log into the service. For example, a compromised login page may log provided user credentials before logging the user in to the service.

This variation on input capture may be conducted post-compromise using legitimate administrative access as a backup measure to maintain network access through [External Remote Services](https://attack.mitre.org/techniques/T1133) and [Valid Accounts](https://attack.mitre.org/techniques/T1078) or as part of the initial compromise by exploitation of the externally facing web service.(Citation: Volexity Virtual Private Keylogging)

File monitoring may be used to detect changes to files in the Web directory for organization login pages that do not match with authorized updates to the Web server's content.


Inter-Process Communication

Adversaries may abuse inter-process communication (IPC) mechanisms for local code or command execution. IPC is typically used by processes to share data, communicate with each other, or synchronize execution. IPC is also commonly used to avoid situations such as deadlocks, which occurs when processes are stuck in a cyclic waiting pattern.

Adversaries may abuse IPC to execute arbitrary code or commands. IPC mechanisms may differ depending on OS, but typically exists in a form accessible through programming languages/libraries or native interfaces such as Windows [Dynamic Data Exchange](https://attack.mitre.org/techniques/T1559/002) or [Component Object Model](https://attack.mitre.org/techniques/T1559/001). Linux environments support several different IPC mechanisms, two of which being sockets and pipes.(Citation: Linux IPC) Higher level execution mediums, such as those of [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059)s, may also leverage underlying IPC mechanisms. Adversaries may also use [Remote Services](https://attack.mitre.org/techniques/T1021) such as [Distributed Component Object Model](https://attack.mitre.org/techniques/T1021/003) to facilitate remote IPC execution.(Citation: Fireeye Hunting COM June 2019)

Monitor for strings in files/commands, loaded DLLs/libraries, or spawned processes that are associated with abuse of IPC mechanisms.


Inter-Process Communication: Component Object Model

Adversaries may use the Windows Component Object Model (COM) for local code execution. COM is an inter-process communication (IPC) component of the native Windows application programming interface (API) that enables interaction between software objects, or executable code that implements one or more interfaces.(Citation: Fireeye Hunting COM June 2019) Through COM, a client object can call methods of server objects, which are typically binary Dynamic Link Libraries (DLL) or executables (EXE).(Citation: Microsoft COM) Remote COM execution is facilitated by [Remote Services](https://attack.mitre.org/techniques/T1021) such as  [Distributed Component Object Model](https://attack.mitre.org/techniques/T1021/003) (DCOM).(Citation: Fireeye Hunting COM June 2019)

Various COM interfaces are exposed that can be abused to invoke arbitrary execution via a variety of programming languages such as C, C++, Java, and [Visual Basic](https://attack.mitre.org/techniques/T1059/005).(Citation: Microsoft COM) Specific COM objects also exist to directly perform functions beyond code execution, such as creating a [Scheduled Task/Job](https://attack.mitre.org/techniques/T1053), fileless download/execution, and other adversary behaviors related to privilege escalation and persistence.(Citation: Fireeye Hunting COM June 2019)(Citation: ProjectZero File Write EoP Apr 2018)

Monitor for COM objects loading DLLs and other modules not typically associated with the application.(Citation: Enigma Outlook DCOM Lateral Movement Nov 2017) Enumeration of COM objects, via [Query Registry](https://attack.mitre.org/techniques/T1012) or [PowerShell](https://attack.mitre.org/techniques/T1059/001), may also proceed malicious use.(Citation: Fireeye Hunting COM June 2019)(Citation: Enigma MMC20 COM Jan 2017)

Monitor for spawning of processes associated with COM objects, especially those invoked by a user different than the one currently logged on.


Inter-Process Communication: Dynamic Data Exchange

Adversaries may use Windows Dynamic Data Exchange (DDE) to execute arbitrary commands. DDE is a client-server protocol for one-time and/or continuous inter-process communication (IPC) between applications. Once a link is established, applications can autonomously exchange transactions consisting of strings, warm data links (notifications when a data item changes), hot data links (duplications of changes to a data item), and requests for command execution.

Object Linking and Embedding (OLE), or the ability to link data between documents, was originally implemented through DDE. Despite being superseded by [Component Object Model](https://attack.mitre.org/techniques/T1559/001), DDE may be enabled in Windows 10 and most of Microsoft Office 2016 via Registry keys.(Citation: BleepingComputer DDE Disabled in Word Dec 2017)(Citation: Microsoft ADV170021 Dec 2017)(Citation: Microsoft DDE Advisory Nov 2017)

Microsoft Office documents can be poisoned with DDE commands, directly or through embedded files, and used to deliver execution via [Phishing](https://attack.mitre.org/techniques/T1566) campaigns or hosted Web content, avoiding the use of Visual Basic for Applications (VBA) macros.(Citation: SensePost PS DDE May 2016)(Citation: Kettle CSV DDE Aug 2014)(Citation: Enigma Reviving DDE Jan 2018)(Citation: SensePost MacroLess DDE Oct 2017) Similarly, adversaries may infect payloads to execute applications and/or commands on a victim device by way of embedding DDE formulas within a CSV file intended to be opened through a Windows spreadsheet program.(Citation: OWASP CSV Injection)(Citation: CSV Excel Macro Injection )

DDE could also be leveraged by an adversary operating on a compromised machine who does not have direct access to a [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059). DDE execution can be invoked remotely via [Remote Services](https://attack.mitre.org/techniques/T1021) such as [Distributed Component Object Model](https://attack.mitre.org/techniques/T1021/003) (DCOM).(Citation: Fireeye Hunting COM June 2019)

Monitor processes for abnormal behavior indicative of DDE abuse, such as Microsoft Office applications loading DLLs and other modules not typically associated with the application or these applications spawning unusual processes (such as cmd.exe).

OLE, Office Open XML, CSV, and other files can be scanned for ‘DDEAUTO', ‘DDE’, and other strings indicative of DDE execution.(Citation: NVisio Labs DDE Detection Oct 2017)(Citation: OWASP CSV Injection)(Citation: CSV Excel Macro Injection )


Inter-Process Communication: XPC Services

Adversaries can provide malicious content to an XPC service daemon for local code execution. macOS uses XPC services for basic inter-process communication between various processes, such as between the XPC Service daemon and third-party application privileged helper tools. Applications can send messages to the XPC Service daemon, which runs as root, using the low-level XPC Service C API or the high level NSXPCConnection API in order to handle tasks that require elevated privileges (such as network connections). Applications are responsible for providing the protocol definition which serves as a blueprint of the XPC services. Developers typically use XPC Services to provide applications stability and privilege separation between the application client and the daemon.(Citation: creatingXPCservices)(Citation: Designing Daemons Apple Dev)

Adversaries can abuse XPC services to execute malicious content. Requests for malicious execution can be passed through the application's XPC Services handler.(Citation: CVMServer Vuln)(Citation: Learn XPC Exploitation) This may also include identifying and abusing improper XPC client validation and/or poor sanitization of input parameters to conduct [Exploitation for Privilege Escalation](https://attack.mitre.org/techniques/T1068).


Internal Spearphishing

After they already have access to accounts or systems within the environment, adversaries may use internal spearphishing to gain access to additional information or compromise other users within the same organization. Internal spearphishing is multi-staged campaign where a legitimate account is initially compromised either by controlling the user's device or by compromising the account credentials of the user. Adversaries may then attempt to take advantage of the trusted internal account to increase the likelihood of tricking more victims into falling for phish attempts, often incorporating [Impersonation](https://attack.mitre.org/techniques/T1656).(Citation: Trend Micro - Int SP)

For example, adversaries may leverage [Spearphishing Attachment](https://attack.mitre.org/techniques/T1566/001) or [Spearphishing Link](https://attack.mitre.org/techniques/T1566/002) as part of internal spearphishing to deliver a payload or redirect to an external site to capture credentials through [Input Capture](https://attack.mitre.org/techniques/T1056) on sites that mimic login interfaces.

Adversaries may also leverage internal chat apps, such as Microsoft Teams, to spread malicious content or engage users in attempts to capture sensitive information and/or credentials.(Citation: Int SP - chat apps)

Network intrusion detection systems and email gateways usually do not scan internal email, but an organization can leverage the journaling-based solution which sends a copy of emails to a security service for offline analysis or incorporate service-integrated solutions using on-premise or API-based integrations to help detect internal spearphishing campaigns.(Citation: Trend Micro When Phishing Starts from the Inside 2017)


Lateral Tool Transfer

Adversaries may transfer tools or other files between systems in a compromised environment. Once brought into the victim environment (i.e., [Ingress Tool Transfer](https://attack.mitre.org/techniques/T1105)) files may then be copied from one system to another to stage adversary tools or other files over the course of an operation.

Adversaries may copy files between internal victim systems to support lateral movement using inherent file sharing protocols such as file sharing over [SMB/Windows Admin Shares](https://attack.mitre.org/techniques/T1021/002) to connected network shares or with authenticated connections via [Remote Desktop Protocol](https://attack.mitre.org/techniques/T1021/001).(Citation: Unit42 LockerGoga 2019)

Files can also be transferred using native or otherwise present tools on the victim system, such as scp, rsync, curl, sftp, and [ftp](https://attack.mitre.org/software/S0095). In some cases, adversaries may be able to leverage [Web Service](https://attack.mitre.org/techniques/T1102)s such as Dropbox or OneDrive to copy files from one machine to another via shared, automatically synced folders.(Citation: Dropbox Malware Sync)

Monitor for file creation and files transferred within a network using protocols such as SMB or FTP. Unusual processes with internal network connections creating files on-system may be suspicious. Consider monitoring for abnormal usage of utilities and command-line arguments that may be used in support of remote transfer of files. Considering monitoring for alike file hashes or characteristics (ex: filename) that are created on multiple hosts.


Log Enumeration

Adversaries may enumerate system and service logs to find useful data. These logs may highlight various types of valuable insights for an adversary, such as user authentication records ([Account Discovery](https://attack.mitre.org/techniques/T1087)), security or vulnerable software ([Software Discovery](https://attack.mitre.org/techniques/T1518)), or hosts within a compromised network ([Remote System Discovery](https://attack.mitre.org/techniques/T1018)).

Host binaries may be leveraged to collect system logs. Examples include using `wevtutil.exe` or [PowerShell](https://attack.mitre.org/techniques/T1059/001) on Windows to access and/or export security event information.(Citation: WithSecure Lazarus-NoPineapple Threat Intel Report 2023)(Citation: Cadet Blizzard emerges as novel threat actor) In cloud environments, adversaries may leverage utilities such as the Azure VM Agent’s `CollectGuestLogs.exe` to collect security logs from cloud hosted infrastructure.(Citation: SIM Swapping and Abuse of the Microsoft Azure Serial Console)

Adversaries may also target centralized logging infrastructure such as SIEMs. Logs may also be bulk exported and sent to adversary-controlled infrastructure for offline analysis.


Masquerading

Adversaries may attempt to manipulate features of their artifacts to make them appear legitimate or benign to users and/or security tools. Masquerading occurs when the name or location of an object, legitimate or malicious, is manipulated or abused for the sake of evading defenses and observation. This may include manipulating file metadata, tricking users into misidentifying the file type, and giving legitimate task or service names.

Renaming abusable system utilities to evade security monitoring is also a form of [Masquerading](https://attack.mitre.org/techniques/T1036).(Citation: LOLBAS Main Site)

Collect file hashes; file names that do not match their expected hash are suspect. Perform file monitoring; files with known names but in unusual locations are suspect. Likewise, files that are modified outside of an update or patch are suspect.

If file names are mismatched between the file name on disk and that of the binary's PE metadata, this is a likely indicator that a binary was renamed after it was compiled. Collecting and comparing disk and resource filenames for binaries by looking to see if the InternalName, OriginalFilename, and/or ProductName match what is expected could provide useful leads, but may not always be indicative of malicious activity. (Citation: Elastic Masquerade Ball) Do not focus on the possible names a file could have, but instead on the command-line arguments that are known to be used and are distinct because it will have a better rate of detection.(Citation: Twitter ItsReallyNick Masquerading Update)

Look for indications of common characters that may indicate an attempt to trick users into misidentifying the file type, such as a space as the last character of a file name or the right-to-left override characters"\u202E", "[U+202E]", and "%E2%80%AE”.


Masquerading: Break Process Trees

An adversary may attempt to evade process tree-based analysis by modifying executed malware's parent process ID (PPID). If endpoint protection software leverages the “parent-child" relationship for detection, breaking this relationship could result in the adversary’s behavior not being associated with previous process tree activity. On Unix-based systems breaking this process tree is common practice for administrators to execute software using scripts and programs.(Citation: 3OHA double-fork 2022)

On Linux systems, adversaries may execute a series of [Native API](https://attack.mitre.org/techniques/T1106) calls to alter malware's process tree. For example, adversaries can execute their payload without any arguments, call the `fork()` API call twice, then have the parent process exit. This creates a grandchild process with no parent process that is immediately adopted by the `init` system process (PID 1), which successfully disconnects the execution of the adversary's payload from its previous process tree.

Another example is using the “daemon” syscall to detach from the current parent process and run in the background.(Citation: Sandfly BPFDoor 2022)(Citation: Microsoft XorDdos Linux Stealth 2022)


Masquerading: Double File Extension

Adversaries may abuse a double extension in the filename as a means of masquerading the true file type. A file name may include a secondary file type extension that may cause only the first extension to be displayed (ex: File.txt.exe may render in some views as just File.txt). However, the second extension is the true file type that determines how the file is opened and executed. The real file extension may be hidden by the operating system in the file browser (ex: explorer.exe), as well as in any software configured using or similar to the system’s policies.(Citation: PCMag DoubleExtension)(Citation: SOCPrime DoubleExtension)

Adversaries may abuse double extensions to attempt to conceal dangerous file types of payloads. A very common usage involves tricking a user into opening what they think is a benign file type but is actually executable code. Such files often pose as email attachments and allow an adversary to gain [Initial Access](https://attack.mitre.org/tactics/TA0001) into a user’s system via [Spearphishing Attachment](https://attack.mitre.org/techniques/T1566/001) then [User Execution](https://attack.mitre.org/techniques/T1204). For example, an executable file attachment named Evil.txt.exe may display as Evil.txt to a user. The user may then view it as a benign text file and open it, inadvertently executing the hidden malware.(Citation: SOCPrime DoubleExtension)

Common file types, such as text files (.txt, .doc, etc.) and image files (.jpg, .gif, etc.) are typically used as the first extension to appear benign. Executable extensions commonly regarded as dangerous, such as .exe, .lnk, .hta, and .scr, often appear as the second extension and true file type.

Monitor for files written to disk that contain two file extensions, particularly when the second is an executable.(Citation: Seqrite DoubleExtension)


Masquerading: Invalid Code Signature

Adversaries may attempt to mimic features of valid code signatures to increase the chance of deceiving a user, analyst, or tool. Code signing provides a level of authenticity on a binary from the developer and a guarantee that the binary has not been tampered with. Adversaries can copy the metadata and signature information from a signed program, then use it as a template for an unsigned program. Files with invalid code signatures will fail digital signature validation checks, but they may appear more legitimate to users and security tools may improperly handle these files.(Citation: Threatexpress MetaTwin 2017)

Unlike [Code Signing](https://attack.mitre.org/techniques/T1553/002), this activity will not result in a valid signature.

Collect and analyze signing certificate metadata and check signature validity on software that executes within the environment, look for invalid signatures as well as unusual certificate characteristics and outliers.


Masquerading: Masquerade File Type

Adversaries may masquerade malicious payloads as legitimate files through changes to the payload's formatting, including the file’s signature, extension, and contents. Various file types have a typical standard format, including how they are encoded and organized. For example, a file’s signature (also known as header or magic bytes) is the beginning bytes of a file and is often used to identify the file’s type. For example, the header of a JPEG file,  is  0xFF 0xD8 and the file extension is either `.JPE`, `.JPEG` or `.JPG`.

Adversaries may edit the header’s hex code and/or the file extension of a malicious payload in order to bypass file validation checks and/or input sanitization. This behavior is commonly used when payload files are transferred (e.g., [Ingress Tool Transfer](https://attack.mitre.org/techniques/T1105)) and stored (e.g., [Upload Malware](https://attack.mitre.org/techniques/T1608/001)) so that adversaries may move their malware without triggering detections.

Common non-executable file types and extensions, such as text files (`.txt`) and image files (`.jpg`, `.gif`, etc.) may be typically treated as benign.  Based on this, adversaries may use a file extension to disguise malware, such as naming a PHP backdoor code with a file name of test.gif. A user may not know that a file is malicious due to the benign appearance and file extension.

Polygot files, which are files that have multiple different file types and that function differently based on the application that will execute them, may also be used to disguise malicious malware and capabilities.(Citation: polygot_icedID)


Masquerading: Masquerade Task or Service

Adversaries may attempt to manipulate the name of a task or service to make it appear legitimate or benign. Tasks/services executed by the Task Scheduler or systemd will typically be given a name and/or description.(Citation: TechNet Schtasks)(Citation: Systemd Service Units) Windows services will have a service name as well as a display name. Many benign tasks and services exist that have commonly associated names. Adversaries may give tasks or services names that are similar or identical to those of legitimate ones.

Tasks or services contain other fields, such as a description, that adversaries may attempt to make appear legitimate.(Citation: Palo Alto Shamoon Nov 2016)(Citation: Fysbis Dr Web Analysis)

Look for changes to tasks and services that do not correlate with known software, patch cycles, etc. Suspicious program execution through scheduled tasks or services may show up as outlier processes that have not been seen before when compared against historical data. Monitor processes and command-line arguments for actions that could be taken to create tasks or services. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.


Masquerading: Match Legitimate Name or Location

Adversaries may match or approximate the name or location of legitimate files or resources when naming/placing them. This is done for the sake of evading defenses and observation. This may be done by placing an executable in a commonly trusted directory (ex: under System32) or giving it the name of a legitimate, trusted program (ex: svchost.exe). In containerized environments, this may also be done by creating a resource in a namespace that matches the naming convention of a container pod or cluster. Alternatively, a file or container image name given may be a close approximation to legitimate programs/images or something innocuous.

Adversaries may also use the same icon of the file they are trying to mimic.

Collect file hashes; file names that do not match their expected hash are suspect. Perform file monitoring; files with known names but in unusual locations are suspect. Likewise, files that are modified outside of an update or patch are suspect.

If file names are mismatched between the file name on disk and that of the binary's PE metadata, this is a likely indicator that a binary was renamed after it was compiled. Collecting and comparing disk and resource filenames for binaries by looking to see if the InternalName, OriginalFilename, and/or ProductName match what is expected could provide useful leads, but may not always be indicative of malicious activity. (Citation: Elastic Masquerade Ball) Do not focus on the possible names a file could have, but instead on the command-line arguments that are known to be used and are distinct because it will have a better rate of detection.(Citation: Twitter ItsReallyNick Masquerading Update)

In containerized environments, use image IDs and layer hashes to compare images instead of relying only on their names.(Citation: Docker Images) Monitor for the unexpected creation of new resources within your cluster in Kubernetes, especially those created by atypical users.


Masquerading: Rename System Utilities

Adversaries may rename legitimate system utilities to try to evade security mechanisms concerning the usage of those utilities. Security monitoring and control mechanisms may be in place for system utilities adversaries are capable of abusing. (Citation: LOLBAS Main Site) It may be possible to bypass those security mechanisms by renaming the utility prior to utilization (ex: rename rundll32.exe). (Citation: Elastic Masquerade Ball) An alternative case occurs when a legitimate utility is copied or moved to a different directory and renamed to avoid detections based on system utilities executing from non-standard paths. (Citation: F-Secure CozyDuke)

If file names are mismatched between the file name on disk and that of the binary's PE metadata, this is a likely indicator that a binary was renamed after it was compiled. Collecting and comparing disk and resource filenames for binaries by looking to see if the InternalName, OriginalFilename, and/or ProductName match what is expected could provide useful leads, but may not always be indicative of malicious activity. (Citation: Elastic Masquerade Ball) Do not focus on the possible names a file could have, but instead on the command-line arguments that are known to be used and are distinct because it will have a better rate of detection.(Citation: Twitter ItsReallyNick Masquerading Update)


Masquerading: Right-to-Left Override

Adversaries may abuse the right-to-left override (RTLO or RLO) character (U+202E) to disguise a string and/or file name to make it appear benign. RTLO is a non-printing Unicode character that causes the text that follows it to be displayed in reverse. For example, a Windows screensaver executable named March 25 \u202Excod.scr will display as March 25 rcs.docx. A JavaScript file named photo_high_re\u202Egnp.js will be displayed as photo_high_resj.png.(Citation: Infosecinstitute RTLO Technique)

Adversaries may abuse the RTLO character as a means of tricking a user into executing what they think is a benign file type. A common use of this technique is with [Spearphishing Attachment](https://attack.mitre.org/techniques/T1566/001)/[Malicious File](https://attack.mitre.org/techniques/T1204/002) since it can trick both end users and defenders if they are not aware of how their tools display and render the RTLO character. Use of the RTLO character has been seen in many targeted intrusion attempts and criminal activity.(Citation: Trend Micro PLEAD RTLO)(Citation: Kaspersky RTLO Cyber Crime) RTLO can be used in the Windows Registry as well, where regedit.exe displays the reversed characters but the command line tool reg.exe does not by default.

Detection methods should include looking for common formats of RTLO characters within filenames such as \u202E, [U+202E], and %E2%80%AE. Defenders should also check their analysis tools to ensure they do not interpret the RTLO character and instead print the true name of the file containing it.


Masquerading: Space after Filename

Adversaries can hide a program's true filetype by changing the extension of a file. With certain file types (specifically this does not work with .app extensions), appending a space to the end of a filename will change how the file is processed by the operating system.

For example, if there is a Mach-O executable file called evil.bin, when it is double clicked by a user, it will launch Terminal.app and execute. If this file is renamed to evil.txt, then when double clicked by a user, it will launch with the default text editing application (not executing the binary). However, if the file is renamed to evil.txt  (note the space at the end), then when double clicked by a user, the true file type is determined by the OS and handled appropriately and the binary will be executed (Citation: Mac Backdoors are back).

Adversaries can use this feature to trick users into double clicking benign-looking files of any format and ultimately executing something malicious.

It's not common for spaces to be at the end of filenames, so this is something that can easily be checked with file monitoring. From the user's perspective though, this is very hard to notice from within the Finder.app or on the command-line in Terminal.app. Processes executed from binaries containing non-standard extensions in the filename are suspicious.


Modify Authentication Process

Adversaries may modify authentication mechanisms and processes to access user credentials or enable otherwise unwarranted access to accounts. The authentication process is handled by mechanisms, such as the Local Security Authentication Server (LSASS) process and the Security Accounts Manager (SAM) on Windows, pluggable authentication modules (PAM) on Unix-based systems, and authorization plugins on MacOS systems, responsible for gathering, storing, and validating credentials. By modifying an authentication process, an adversary may be able to authenticate to a service or system without using [Valid Accounts](https://attack.mitre.org/techniques/T1078).

Adversaries may maliciously modify a part of this process to either reveal credentials or bypass authentication mechanisms. Compromised credentials or access may be used to bypass access controls placed on various resources on systems within the network and may even be used for persistent access to remote systems and externally available services, such as VPNs, Outlook Web Access and remote desktop.

Credential Access, Defense Evasion, Persistence

Monitor for new, unfamiliar DLL files written to a domain controller and/or local computer. Monitor for changes to Registry entries for password filters (ex: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Notification Packages) and correlate then investigate the DLL files these files reference.

Password filters will also show up as an autorun and loaded DLL in lsass.exe.(Citation: Clymb3r Function Hook Passwords Sept 2013)

Monitor for calls to OpenProcess that can be used to manipulate lsass.exe running on a domain controller as well as for malicious modifications to functions exported from authentication-related system DLLs (such as cryptdll.dll and samsrv.dll).(Citation: Dell Skeleton)

Monitor PAM configuration and module paths (ex: /etc/pam.d/) for changes. Use system-integrity tools such as AIDE and monitoring tools such as auditd to monitor PAM files.

Monitor for suspicious additions to the /Library/Security/SecurityAgentPlugins directory.(Citation: Xorrior Authorization Plugins)

Configure robust, consistent account activity audit policies across the enterprise and with externally accessible services. (Citation: TechNet Audit Policy) Look for suspicious account behavior across systems that share accounts, either user, admin, or service accounts. Examples: one account logged into multiple systems simultaneously; multiple accounts logged into the same machine simultaneously; accounts logged in at odd times or outside of business hours. Activity may be from interactive login sessions or process ownership from accounts being used to execute binaries on a remote system as a particular account. Correlate other security systems with login information (e.g., a user has an active login session but has not entered the building or does not have VPN access).

Monitor property changes in Group Policy that manage authentication mechanisms (i.e. [Group Policy Modification](https://attack.mitre.org/techniques/T1484/001)). The Store passwords using reversible encryption configuration should be set to Disabled. Additionally, monitor and/or block suspicious command/script execution of -AllowReversiblePasswordEncryption $true, Set-ADUser and Set-ADAccountControl. Finally, monitor Fine-Grained Password Policies and regularly audit user accounts and group settings.(Citation: dump_pwd_dcsync)


Modify Authentication Process: Conditional Access Policies

Adversaries may disable or modify conditional access policies to enable persistent access to compromised accounts. Conditional access policies are additional verifications used by identity providers and identity and access management systems to determine whether a user should be granted access to a resource.

For example, in Azure AD, Okta, and JumpCloud, users can be denied access to applications based on their IP address, device enrollment status, and use of multi-factor authentication.(Citation: Microsoft Conditional Access)(Citation: JumpCloud Conditional Access Policies)(Citation: Okta Conditional Access Policies) In some cases, identity providers may also support the use of risk-based metrics to deny sign-ins based on a variety of indicators. In AWS and GCP, IAM policies can contain `condition` attributes that verify arbitrary constraints such as the source IP, the date the request was made, and the nature of the resources or regions being requested.(Citation: AWS IAM Conditions)(Citation: GCP IAM Conditions) These measures help to prevent compromised credentials from resulting in unauthorized access to data or resources, as well as limit user permissions to only those required.

By modifying conditional access policies, such as adding additional trusted IP ranges, removing [Multi-Factor Authentication](https://attack.mitre.org/techniques/T1556/006) requirements, or allowing additional [Unused/Unsupported Cloud Regions](https://attack.mitre.org/techniques/T1535), adversaries may be able to ensure persistent access to accounts and circumvent defensive measures.


Modify Authentication Process: Domain Controller Authentication

Adversaries may patch the authentication process on a domain controller to bypass the typical authentication mechanisms and enable access to accounts.

Malware may be used to inject false credentials into the authentication process on a domain controller with the intent of creating a backdoor used to access any user’s account and/or credentials (ex: [Skeleton Key](https://attack.mitre.org/software/S0007)). Skeleton key works through a patch on an enterprise domain controller authentication process (LSASS) with credentials that adversaries may use to bypass the standard authentication system. Once patched, an adversary can use the injected password to successfully authenticate as any domain user account (until the the skeleton key is erased from memory by a reboot of the domain controller). Authenticated access may enable unfettered access to hosts and/or resources within single-factor authentication environments.(Citation: Dell Skeleton)

Monitor for calls to OpenProcess that can be used to manipulate lsass.exe running on a domain controller as well as for malicious modifications to functions exported from authentication-related system DLLs (such as cryptdll.dll and samsrv.dll).(Citation: Dell Skeleton)

Configure robust, consistent account activity audit policies across the enterprise and with externally accessible services.(Citation: TechNet Audit Policy) Look for suspicious account behavior across systems that share accounts, either user, admin, or service accounts. Examples: one account logged into multiple systems simultaneously; multiple accounts logged into the same machine simultaneously; accounts logged in at odd times or outside of business hours. Activity may be from interactive login sessions or process ownership from accounts being used to execute binaries on a remote system as a particular account. Correlate other security systems with login information (e.g. a user has an active login session but has not entered the building or does not have VPN access).


Modify Authentication Process: Hybrid Identity

Adversaries may patch, modify, or otherwise backdoor cloud authentication processes that are tied to on-premises user identities in order to bypass typical authentication mechanisms, access credentials, and enable persistent access to accounts.

Many organizations maintain hybrid user and device identities that are shared between on-premises and cloud-based environments. These can be maintained in a number of ways. For example, Azure AD includes three options for synchronizing identities between Active Directory and Azure AD(Citation: Azure AD Hybrid Identity):

* Password Hash Synchronization (PHS), in which a privileged on-premises account synchronizes user password hashes between Active Directory and Azure AD, allowing authentication to Azure AD to take place entirely in the cloud
* Pass Through Authentication (PTA), in which Azure AD authentication attempts are forwarded to an on-premises PTA agent, which validates the credentials against Active Directory
* Active Directory Federation Services (AD FS), in which a trust relationship is established between Active Directory and Azure AD

AD FS can also be used with other SaaS and cloud platforms such as AWS and GCP, which will hand off the authentication process to AD FS and receive a token containing the hybrid users’ identity and privileges.

By modifying authentication processes tied to hybrid identities, an adversary may be able to establish persistent privileged access to cloud resources. For example, adversaries who compromise an on-premises server running a PTA agent may inject a malicious DLL into the `AzureADConnectAuthenticationAgentService` process that authorizes all attempts to authenticate to Azure AD, as well as records user credentials.(Citation: Azure AD Connect for Read Teamers)(Citation: AADInternals Azure AD On-Prem to Cloud) In environments using AD FS, an adversary may edit the `Microsoft.IdentityServer.Servicehost` configuration file to load a malicious DLL that generates authentication tokens for any user with any set of claims, thereby bypassing multi-factor authentication and defined AD FS policies.(Citation: MagicWeb)

In some cases, adversaries may be able to modify the hybrid identity authentication process from the cloud. For example, adversaries who compromise a Global Administrator account in an Azure AD tenant may be able to register a new PTA agent via the web console, similarly allowing them to harvest credentials and log into the Azure AD environment as any user.(Citation: Mandiant Azure AD Backdoors)


Modify Authentication Process: Multi-Factor Authentication

Adversaries may disable or modify multi-factor authentication (MFA) mechanisms to enable persistent access to compromised accounts.

Once adversaries have gained access to a network by either compromising an account lacking MFA or by employing an MFA bypass method such as [Multi-Factor Authentication Request Generation](https://attack.mitre.org/techniques/T1621), adversaries may leverage their access to modify or completely disable MFA defenses. This can be accomplished by abusing legitimate features, such as excluding users from Azure AD Conditional Access Policies, registering a new yet vulnerable/adversary-controlled MFA method, or by manually patching MFA programs and configuration files to bypass expected functionality.(Citation: Mandiant APT42)(Citation: Azure AD Conditional Access Exclusions)

For example, modifying the Windows hosts file (`C:\windows\system32\drivers\etc\hosts`) to redirect MFA calls to localhost instead of an MFA server may cause the MFA process to fail. If a "fail open" policy is in place, any otherwise successful authentication attempt may be granted access without enforcing MFA. (Citation: Russians Exploit Default MFA Protocol - CISA March 2022)

Depending on the scope, goals, and privileges of the adversary, MFA defenses may be disabled for individual accounts or for all accounts tied to a larger group, such as all domain accounts in a victim's network environment.(Citation: Russians Exploit Default MFA Protocol - CISA March 2022)


Modify Authentication Process: Network Device Authentication

Adversaries may use [Patch System Image](https://attack.mitre.org/techniques/T1601/001) to hard code a password in the operating system, thus bypassing of native authentication mechanisms for local accounts on network devices.

[Modify System Image](https://attack.mitre.org/techniques/T1601) may include implanted code to the operating system for network devices to provide access for adversaries using a specific password.  The modification includes a specific password which is implanted in the operating system image via the patch.  Upon authentication attempts, the inserted code will first check to see if the user input is the password. If so, access is granted. Otherwise, the implanted code will pass the credentials on for verification of potentially valid credentials.(Citation: Mandiant - Synful Knock)

Consider verifying the checksum of the operating system file and verifying the image of the operating system in memory.(Citation: Cisco IOS Software Integrity Assurance - Image File Verification)(Citation: Cisco IOS Software Integrity Assurance - Run-Time Memory Verification)

Detection of this behavior may be difficult, detection efforts may be focused on closely related adversary behaviors, such as [Modify System Image](https://attack.mitre.org/techniques/T1601).