Query: Encoded PowerShell / command-line abuse matching Disable or Modify Windows Event Log
Matching 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
Near-miss passage: T1685 Disable or Modify Tools. Tactics: defense impairment. Description: Adversaries may disable, degrade, or tamper with security tools or applications (e.g., endpoint detection and response (EDR) tools, intrusion detection systems (IDS), antivirus, logging agents, sensors, etc.) to impair or reduce visibility of defensive capabilities. This may include stopping specific services, killing processes, modifying or deleting tool configuration files and Registry keys, or preventing tools from updating. This may also include impairing defenses more broadly by disrupting preventative, detection, and response mechanisms across host, network, and cloud environments.(Citation: SCADAfence_ransomware) In addition to directly targeting tools, adversaries may block or manipulate indicators and telemetry used for detection. This includes maliciously disabling or redirecting sensors such as Event Tracing for Windows (ETW), modifying event log configurations (e.g., redirecting Security logs), or interfering with logging pipelines and forwarding mechanisms (e.g., SIEM ingestion).(Citation: Microsoft Lamin Sept 2017)(Citation: ETW Palantir) More advanced techniques include leveraging legitimate drivers or debugging mechanisms to render tools non-functional, bypassing anti-tampering protections, and targeting specific defenses such as Sysmon or cloud monitoring agents. Adversaries may also disrupt broader defensive operations, including update mechanisms, logging infrastructure (e.g., syslog), or event aggregation, further degrading an organization’s ability to detect and respond to malicious activity.(Citation: Cocomazzi FIN7 Reboot)