Query: EDR alert: possible Disable or Modify Linux Audit System Log (T1685.004)
Matching passage: T1685.004 Disable or Modify Linux Audit System Log. Tactics: defense impairment. Description: 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: IzyKnows auditd threat detection 2022)(Citation: Red Hat Linux Disable or Mod) 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: ESET Ebury Feb 2014)
Near-miss passage: T1685.001 Disable or Modify Windows Event Log. Tactics: defense impairment. Description: Adversaries may disable or modify the Windows Event Log to limit data that can be leveraged for detections and audits. Windows Event Log records user and system activity such as login attempts and process creation.(Citation: EventLog_Core_Technologies) This data is used by security tools and analysts to generate detections. The EventLog service maintains event logs from various system components and applications. 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: Microsoft Audit Policy)(Citation: Microsoft Adv Security Settings) `auditpol.exe` may also be used to set audit policies.(Citation: Microsoft 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`). 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_Event_Logging)(Citation: disable_win_evt_logging) There are several ways to disable the EventLog service via registry key modification. 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) W