Malicious ShellIntel PowerShell Commandlets
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In this page
Rule name | Rule type | Log sources | MITRE ATT&CK tags | Severity |
Malicious ShellIntel PowerShell Commandlets | Standard | Windows | Execution: Command and Scripting Interpreter - PowerShell (T1059.001) | Critical |
About the rule
Rule Type
Standard
Rule Description
ShellIntel is a post-exploitation PowerShell framework that provides attackers with scripts for privilege escalation, credential access, and enumeration. Malicious actors may abuse commandlets like Invoke-SMBAutoBrute to brute-force SMB credentials, Invoke-GPOLinks to identify weak Group Policy Objects, and Invoke-Potato for exploiting privilege escalation vulnerabilities on misconfigured systems.
Severity
Trouble
Rule journey
Attack chain scenario
Unpatched VPN gateway exploited → Attacker drops PowerShell payload → ShellIntel script runs to scan SMB for weak creds → Admin-level credentials reused to access internal server → Sensitive data archived and exfiltrated
Impact
- Exposure of administrative credentials
- Unauthorized access to Group Policy configurations
- Domain compromise
- Data exfiltration
Rule Requirement
Prerequisites
Logon to Group Policy Management Console with administrative privileges and enable Module Logging for Windows PowerShell in the Group Policy Management Editor. Ensure to enter * in the Module Names window to record all modules. Similarly enable PowerShell Script Block Logging for Windows PowerShell. Finally, create a new registry key "Microsoft-Windows-Powershell/Operational" in the directory "Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\".
Criteria
Action1: actionname = "PowerShell Script Block Logged" AND SCRIPTEXECUTED contains "Invoke-SMBAutoBrute,Invoke-GPOLinks,Invoke-Potato" select Action1.HOSTNAME,Action1.MESSAGE,Action1.SCRIPTEXECUTED
Detection
Execution Mode
realtime
Log Sources
Windows
MITRE ATT&CK
Execution: Command and Scripting Interpreter - PowerShell (T1059.001)
Security Standards
Enabling this rule will help you meet the security standard's requirement listed below:
DE.CM-09: Computing hardware and software, runtime environments, and their data are monitored to find potentially adverse events.
When this rule is triggered, you're notified of the use of specific ShellIntel commandlets often linked to post-compromise activity.. This enables you to apply least privilege access for domain and local admin accounts.
Author
Max Altgelt (Nextron Systems), Tobias Michalski (Nextron Systems)
Future actions
Known False Positives
This rule might be triggered due to custom scripts which are used for debugging or memory diagnostics.
Next Steps
When this rule is triggered, the following measures can be implemented:
- Identification: Identify if the flagged event is a new incident or part of an existing incident.
- Analysis: Analyze the impact and extent of the incident to comprehend the severity of the attack using the Incident Workbench.
- Response: Respond promptly by initiating an automated workflow to interrupt the network connections and cease the malicious process.
- Audit PowerShell activities: Implement logging via Script Block Logging and Module Logging.
Mitigation
Mitigation ID | Mitigation Name | Mitigation description |
M1049 | Implement antivirus or antimalware scanning to isolate suspicious files. | |
M1045 | Configure policies that allow PowerShell to execute only signed scripts. | |
M1042 | Restrict or disable PowerShell on systems where it is not required. | |
M1038 | Restrict the execution of scripts that contain sensitive language elements i.e., malicious codes using the PowerShell Constrained Language mode. | |
M1026 | Restrict privileges to execute PowerShell scripts to administrators and enforce limitations on the commands that can be executed via remote PowerShell sessions. |
