Lace Tempest PowerShell Launcher

About the rule

Rule Type

Standard

Rule Description

Lace Tempest is an APT group known for using a PowerShell Launcher targeting SysAid software. By exploiting CVE-2023-47246, a vulnerability in SysAid on-premises, the threat group executes a PowerShell script that launches a malware loader on the victim’s system. This rule detects the execution of such PowerShell scripts associated with Lace Tempest’s PowerShell Launcher.

Severity

Trouble

Rule journey

Attack chain scenario

Initial access → Exploit Public-Facing Application → Execution → PowerShell script execution → Impact

Impact

• Exploitation of vulnerabilities
• Malware execution
• Persistence

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\".

(((( SCRIPTEXECUTED CONTAINS ""\\sysaidserver\\tomcat\\webapps"" ) AND( SCRIPTEXECUTED CONTAINS ""starting user.exe"" ) AND( SCRIPTEXECUTED CONTAINS ""\\usersfiles\\user.exe"" ) AND( SCRIPTEXECUTED CONTAINS ""remove-item -force \""$wapps"" ) AND( SCRIPTEXECUTED CONTAINS ""(sophos)."" ) )))

This rule is triggered when the executed script contains the following suspicious elements:

• \\sysaidserver\\tomcat\\webapps: A file path indicating the location where the script execution occurred.
• starting user.exe: Indicates the execution of user.exe, a malicious process.
• \\usersfiles\\user.exe: A file path indicating the storage location of user.exe file.
• remove-item -force "$wapps": A PowerShell command used to force delete files in the Web Application directory.
• (sophos): Refers to Sophos, an antivirus solution, to indicate potential attempts to evade detection.

Criteria

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 a PowerShell script execution involving Lace Tempest's Launcher. This enables you to monitor runtime environments like PowerShell, detect attempts to exploit CVE-2023-47246, and identify the execution of malware launcher scripts.

Author

Nasreddine Bencherchali (Nextron Systems)

Future actions

Known False Positives

This rule might be triggered when admins execute automated PowerShell scripts for legitimate software upgrades and patch updates.

Next Steps

When this rule is triggered, the following measures can be implemented:

1. Identification: Identify if the flagged event is a new incident or part of an existing incident.
2. Analysis: Analyze the impact and extent of the incident to comprehend the severity of the attack using the Incident Workbench.
3. Response: Respond promptly by initiating an automated workflow to interrupt the network connections and cease the malicious process.
4. Audit PowerShell activities: Continuously monitor PowerShell executions, restrict script execution privileges to administrators only, and disable PowerShell on devices where it is not required.

Mitigation