Name:Malicious PowerShell Process - Encoded Command id:c4db14d9-7909-48b4-a054-aa14d89dbb19 version:11 date:2024-10-17 author:David Dorsey, Michael Haag, Splunk, SirDuckly, GitHub Community status:production type:Hunting 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 is 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. Data_source:
-Sysmon EventID 1
-Windows Event Log Security 4688
-CrowdStrike ProcessRollup2
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` by Processes.user Processes.process_name Processes.process Processes.parent_process_name Processes.original_file_name Processes.dest Processes.process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | where match(process,"(?i)[\-|\/|–|—|―][Ee^]{1,2}[NnCcOoDdEeMmAa^]+\s+[\"]?[A-Za-z0-9+/=]{5,}[\"]?") | `malicious_powershell_process___encoded_command_filter`
how_to_implement:The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process. known_false_positives:System administrators may use this option, but it's not common. References: -https://regexr.com/662ov -https://github.com/redcanaryco/AtomicTestHarnesses/blob/master/Windows/TestHarnesses/T1059.001_PowerShell/OutPowerShellCommandLineParameter.ps1 -https://ss64.com/ps/powershell.html -https://twitter.com/M_haggis/status/1440758396534214658?s=20 -https://www.microsoft.com/security/blog/2022/01/15/destructive-malware-targeting-ukrainian-organizations/ -https://www.microsoft.com/en-us/security/blog/2023/05/24/volt-typhoon-targets-us-critical-infrastructure-with-living-off-the-land-techniques/ drilldown_searches:
: tags: analytic_story: - 'Hermetic Wiper' - 'Malicious PowerShell' - 'NOBELIUM Group' - 'WhisperGate' - 'DarkCrystal RAT' - 'Qakbot' - 'CISA AA22-320A' - 'Sandworm Tools' - 'Data Destruction' - 'Volt Typhoon' - 'Lumma Stealer' asset_type:Endpoint confidence:50 impact:70 message:Powershell.exe running potentially malicious encoded commands on $dest$ mitre_attack_id: - 'T1027' observable: name:'dest' type:'Endpoint' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Processes.process_name' - 'Processes.process' - 'Processes.user' - 'Processes.parent_process_name' - 'Processes.dest' - 'Processes.process_id' risk_score:35 security_domain:endpoint
