MediumSplunk security content David Dorsey +4Threat hunting

Malicious PowerShell Process - Encoded Command

Description

The following analytic detects the use of the EncodedCommand parameter in PowerShell processes. It leverages Endpoint Detection and Response (EDR) data to identify variations of the EncodedCommand parameter, including shortened forms and different command switch types. This activity can be significant because adversaries often use encoded commands to obfuscate malicious scripts, making detection harder. If confirmed malicious, this behavior could allow attackers to execute hidden code, potentially leading to unauthorized access, privilege escalation, or persistent threats within the environment. Review parallel events to determine legitimacy and tune based on known administrative scripts.

Detection logic

Detection requirements

Platform: ESXi Linux macOS Network Devices Windows
The rule states no platform. This is derived from the ATT&CK technique it maps to.
Log source category: crowdstrike_processrollup2 sysmon_eventid_1 windows_event_log_security_4688

Known benign triggers

False positives are expected from legitimate PowerShell scripts, system administrators, and applications. Filter as needed.

References

Links the source published beside this detection. Reference is the link the source wrote, unmodified. Class is decided by this catalogue from the host and path, not stated by the source. Cited by counts published detections citing the same resource, including this one, and the sources beneath it count the repositories this catalogue ingests, which is not the same as independent research.
Reference	Class	Cited by
github.com/redcanaryco/AtomicTestHarnesses/blob/master/Windows/TestHarnesses/T1059.001_PowerShell/OutPowerShellCommandLineParameter.ps1	Tool	Only this detection cites it
github.com/redcanaryco/atomic-red-team/blob/388942adbd9641f4dfdcf079d7efe9a75ec0ac43/atomics/T1027/T1027.yaml#L39	Detection test	3
regexr.com/662ov	Unclassified	Only this detection cites it
ss64.com/ps/powershell.html	Unclassified	Only this detection cites it
twitter.com/M_haggis/status/1440758396534214658?s=20	Social post	Only this detection cites it
www.microsoft.com/en-us/security/blog/2023/05/24/volt-typhoon-targets-us-critical-infrastructure-with-living-off-the-land-techniques/	Threat report	20
www.microsoft.com/security/blog/2022/01/15/destructive-malware-targeting-ukrainian-organizations/	Threat report	27from 2 sources

Detection rules

Malicious PowerShell Process - Encoded Command

Description

Detection logic

Detection requirements

Known benign triggers

MITRE ATT&CK mappings

References

From the source

Licence

Authorship

Detection rules