SLServer dialog remains

Hunt Hypothesis

The SLServer dialog remains detection rule identifies potential adversary persistence by maintaining a long-running dialog process, which may indicate unauthorized access or command and control activity. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate stealthy, long-term adversary presence within the environment.

YARA Rule

rule SLServer_dialog_remains
{
    
    meta:
        author = "Matt Brooks, @cmatthewbrooks"
        desc = "Searches for related dialog remnants."
        ref = "https://citizenlab.org/2016/04/between-hong-kong-and-burma/"
    
    strings:
        $slserver = "SLServer" wide
        
    condition:
        //MZ header //PE signature
        uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550 and $slserver
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A system administrator is performing a scheduled maintenance task that involves keeping the SLServer dialog open temporarily to monitor service status.
  Filter/Exclusion: process.name != "SLServer.exe" OR process.parent.name == "Task Scheduler"

• Scenario: A legitimate security tool or endpoint protection software is interacting with SLServer as part of its normal operation, such as during a scan or policy update.
  Filter/Exclusion: process.name contains "Antivirus" OR process.name contains "Endpoint Protection"

• Scenario: A developer is testing a custom application that communicates with SLServer and intentionally leaves the dialog open to debug or monitor real-time data.
  Filter/Exclusion: process.name contains "Debug" OR process.name contains "Test"

• Scenario: A scheduled job runs a script that interacts with SLServer to generate reports, and the dialog remains open during the job execution.
  Filter/Exclusion: process.name contains "ScheduledTask" OR process.parent.name == "schtasks.exe"

• Scenario: An IT support technician is troubleshooting an issue with SLServer and keeps the dialog open to observe behavior while resolving the problem.
  Filter/Exclusion: process.name contains "Support" OR process.parent.name == "Remote Desktop"