IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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PowerShell Script Block Logging Disabled

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PowerShell Script Block Logging Disabled

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Identifies attempts to disable PowerShell Script Block Logging via registry modification. Attackers may disable this logging to conceal their activities in the host and evade detection.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*
logs-windows.*
endgame-*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://admx.help/?Category=Windows_10_2016&Policy=Microsoft.Policies.PowerShell::EnableScriptBlockLogging

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Defense Evasion
Resources: Investigation Guide
Data Source: Elastic Endgame
Data Source: Elastic Defend

Version: 107

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Triage and analysis

### Investigating PowerShell Script Block Logging Disabled

PowerShell is one of the main tools system administrators use for automation, report routines, and other tasks, making it available in various environments and creating an attractive way for attackers to execute code.

PowerShell Script Block Logging is a feature of PowerShell that records the content of all script blocks that it processes, giving defenders visibility of PowerShell scripts and sequences of executed commands.

#### Possible investigation steps

- Identify the user account that performed the action and whether it should perform this kind of action.
- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Check whether it makes sense for the user to use PowerShell to complete tasks.
- Investigate if PowerShell scripts were run after logging was disabled.

### False positive analysis

- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.

### Related rules

- PowerShell Suspicious Discovery Related Windows API Functions - 61ac3638-40a3-44b2-855a-985636ca985e
- PowerShell Keylogging Script - bd2c86a0-8b61-4457-ab38-96943984e889
- PowerShell Suspicious Script with Audio Capture Capabilities - 2f2f4939-0b34-40c2-a0a3-844eb7889f43
- Potential Process Injection via PowerShell - 2e29e96a-b67c-455a-afe4-de6183431d0d
- Suspicious .NET Reflection via PowerShell - e26f042e-c590-4e82-8e05-41e81bd822ad
- PowerShell Suspicious Payload Encoded and Compressed - 81fe9dc6-a2d7-4192-a2d8-eed98afc766a
- PowerShell Suspicious Script with Screenshot Capabilities - 959a7353-1129-4aa7-9084-30746b256a70

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved hosts to prevent further post-compromise behavior.
- Review the privileges assigned to the involved users to ensure that the least privilege principle is being followed.
- Restrict PowerShell usage outside of IT and engineering business units using GPOs, AppLocker, Intune, or similar software.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).

Rule query

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registry where host.os.type == "windows" and event.type == "change" and
    registry.path : (
        "HKLM\\SOFTWARE\\Policies\\Microsoft\\Windows\\PowerShell\\ScriptBlockLogging\\EnableScriptBlockLogging",
        "\\REGISTRY\\MACHINE\\SOFTWARE\\Policies\\Microsoft\\Windows\\PowerShell\\ScriptBlockLogging\\EnableScriptBlockLogging"
    ) and registry.data.strings : ("0", "0x00000000")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Impair Defenses
- ID: T1562
- Reference URL: https://attack.mitre.org/techniques/T1562/
Sub-technique:
- Name: Disable Windows Event Logging
- ID: T1562.002
- Reference URL: https://attack.mitre.org/techniques/T1562/002/
Technique:
- Name: Modify Registry
- ID: T1112
- Reference URL: https://attack.mitre.org/techniques/T1112/

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