diff --git a/rules/windows/defense_evasion_defender_exclusion_via_powershell.toml b/rules/windows/defense_evasion_defender_exclusion_via_powershell.toml new file mode 100644 index 000000000..cb1807fef --- /dev/null +++ b/rules/windows/defense_evasion_defender_exclusion_via_powershell.toml @@ -0,0 +1,71 @@ +[metadata] +creation_date = "2021/07/20" +maturity = "production" +updated_date = "2021/07/20" + +[rule] +author = ["Elastic"] +description = """ +Identifies modifications to the Windows Defender configuration settings using PowerShell to add exclusions at the folder directory or process level. +""" +from = "now-9m" +index = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*"] +language = "eql" +license = "Elastic License v2" +name = "Windows Defender Exclusions Added via PowerShell" +note = """## Triage and analysis + +Detections should be investigated to identify if the activity corresponds to legitimate activity used to put in exceptions for Windows Defender. As this rule detects post-exploitation process activity, investigations into this should be prioritized""" +references = ["https://www.bitdefender.com/files/News/CaseStudies/study/400/Bitdefender-PR-Whitepaper-MosaicLoader-creat5540-en-EN.pdf"] +risk_score = 47 +rule_id = "2c17e5d7-08b9-43b2-b58a-0270d65ac85b" +severity = "medium" +tags = ["Elastic", "Host", "Windows", "Threat Detection", "Defense Evasion"] +timestamp_override = "event.ingested" +type = "eql" + +query = ''' +process where event.type == "start" and + (process.name : ("powershell.exe", "pwsh.exe") or process.pe.original_file_name : ("powershell.exe", "pwsh.exe")) and + process.args : ("*Add-MpPreference*-Exclusion*", "*Set-MpPreference*-Exclusion*") +''' + + +[[rule.threat]] +framework = "MITRE ATT&CK" +[[rule.threat.technique]] +id = "T1562" +name = "Impair Defenses" +reference = "https://attack.mitre.org/techniques/T1562/" +[[rule.threat.technique.subtechnique]] +id = "T1562.006" +name = "Indicator Blocking" +reference = "https://attack.mitre.org/techniques/T1562/006/" + +[[rule.threat.technique.subtechnique]] +id = "T1562.001" +name = "Disable or Modify Tools" +reference = "https://attack.mitre.org/techniques/T1562/001/" + + + +[rule.threat.tactic] +id = "TA0005" +name = "Defense Evasion" +reference = "https://attack.mitre.org/tactics/TA0005/" +[[rule.threat]] +framework = "MITRE ATT&CK" +[[rule.threat.technique]] +id = "T1059" +name = "Command and Scripting Interpreter" +reference = "https://attack.mitre.org/techniques/T1059/" +[[rule.threat.technique.subtechnique]] +id = "T1059.001" +name = "PowerShell" +reference = "https://attack.mitre.org/techniques/T1059/001/" + + +[rule.threat.tactic] +id = "TA0002" +name = "Execution" +reference = "https://attack.mitre.org/tactics/TA0002/"