PowerShell Script Block Logging Disabled

  1[metadata]
  2creation_date = "2022/01/31"
  3integration = ["endpoint", "windows"]
  4maturity = "production"
  5updated_date = "2024/05/21"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies attempts to disable PowerShell Script Block Logging via registry modification. Attackers may disable this
 11logging to conceal their activities in the host and evade detection.
 12"""
 13from = "now-9m"
 14index = ["winlogbeat-*", "logs-endpoint.events.registry-*", "logs-windows.sysmon_operational-*", "endgame-*"]
 15language = "eql"
 16license = "Elastic License v2"
 17name = "PowerShell Script Block Logging Disabled"
 18note = """## Triage and analysis
 19
 20### Investigating PowerShell Script Block Logging Disabled
 21
 22PowerShell 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.
 23
 24PowerShell 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.
 25
 26#### Possible investigation steps
 27
 28- Identify the user account that performed the action and whether it should perform this kind of action.
 29- 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.
 30- Investigate other alerts associated with the user/host during the past 48 hours.
 31- Check whether it makes sense for the user to use PowerShell to complete tasks.
 32- Investigate if PowerShell scripts were run after logging was disabled.
 33
 34### False positive analysis
 35
 36- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
 37
 38### Related rules
 39
 40- PowerShell Suspicious Discovery Related Windows API Functions - 61ac3638-40a3-44b2-855a-985636ca985e
 41- PowerShell Keylogging Script - bd2c86a0-8b61-4457-ab38-96943984e889
 42- PowerShell Suspicious Script with Audio Capture Capabilities - 2f2f4939-0b34-40c2-a0a3-844eb7889f43
 43- Potential Process Injection via PowerShell - 2e29e96a-b67c-455a-afe4-de6183431d0d
 44- Suspicious .NET Reflection via PowerShell - e26f042e-c590-4e82-8e05-41e81bd822ad
 45- PowerShell Suspicious Payload Encoded and Compressed - 81fe9dc6-a2d7-4192-a2d8-eed98afc766a
 46- PowerShell Suspicious Script with Screenshot Capabilities - 959a7353-1129-4aa7-9084-30746b256a70
 47
 48### Response and remediation
 49
 50- Initiate the incident response process based on the outcome of the triage.
 51- Isolate the involved hosts to prevent further post-compromise behavior.
 52- Review the privileges assigned to the involved users to ensure that the least privilege principle is being followed.
 53- Restrict PowerShell usage outside of IT and engineering business units using GPOs, AppLocker, Intune, or similar software.
 54- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 55- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 56- 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).
 57"""
 58references = [
 59    "https://admx.help/?Category=Windows_10_2016&Policy=Microsoft.Policies.PowerShell::EnableScriptBlockLogging",
 60]
 61risk_score = 47
 62rule_id = "818e23e6-2094-4f0e-8c01-22d30f3506c6"
 63severity = "medium"
 64tags = [
 65    "Domain: Endpoint",
 66    "OS: Windows",
 67    "Use Case: Threat Detection",
 68    "Tactic: Defense Evasion",
 69    "Resources: Investigation Guide",
 70    "Data Source: Elastic Endgame",
 71    "Data Source: Elastic Defend",
 72    "Data Source: Sysmon",
 73]
 74timestamp_override = "event.ingested"
 75type = "eql"
 76
 77query = '''
 78registry where host.os.type == "windows" and event.type == "change" and
 79    registry.path : (
 80        "HKLM\\SOFTWARE\\Policies\\Microsoft\\Windows\\PowerShell\\ScriptBlockLogging\\EnableScriptBlockLogging",
 81        "\\REGISTRY\\MACHINE\\SOFTWARE\\Policies\\Microsoft\\Windows\\PowerShell\\ScriptBlockLogging\\EnableScriptBlockLogging"
 82    ) and registry.data.strings : ("0", "0x00000000")
 83'''
 84
 85
 86[[rule.threat]]
 87framework = "MITRE ATT&CK"
 88[[rule.threat.technique]]
 89id = "T1112"
 90name = "Modify Registry"
 91reference = "https://attack.mitre.org/techniques/T1112/"
 92
 93[[rule.threat.technique]]
 94id = "T1562"
 95name = "Impair Defenses"
 96reference = "https://attack.mitre.org/techniques/T1562/"
 97[[rule.threat.technique.subtechnique]]
 98id = "T1562.002"
 99name = "Disable Windows Event Logging"
100reference = "https://attack.mitre.org/techniques/T1562/002/"
101
102
103
104[rule.threat.tactic]
105id = "TA0005"
106name = "Defense Evasion"
107reference = "https://attack.mitre.org/tactics/TA0005/"