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Another excellent report from The DFIR Report highlights how threat actors are leveraging fake Zoom installers to deploy BlackSuit ransomware. The attackers use sophisticated techniques to evade detection, including process injection and living-off-the-land binaries (LOLBins).
Read the full report here: Fake Zoom Ends in BlackSuit Ransomware
You Should Know:
1. Detecting Malicious MSBuild Activity
Attackers often abuse `msbuild.exe` to execute malicious code. Monitor for unusual `msbuild` processes with suspicious command-line arguments:
Check for unexpected MSBuild processes in Linux (Wine/Cross-Platform) ps aux | grep msbuild Windows Command: tasklist /v | findstr msbuild
2. Analyzing Process Injection
BlackSuit ransomware injects into legitimate processes. Use Sysinternals Process Explorer or PowerShell to detect injected code:
List processes with remote threads (potential injection)
Get-Process | Where-Object { $_.Modules.ModuleName -like "malicious" }
Check for unusual DLLs loaded
tasklist /m
3. Blocking C2 Communications
Since attackers abuse legitimate services (Zoom, Discord, YouTube) for C2, monitor outbound connections:
Linux: Check active connections netstat -tulnp | grep -E 'zoom|discord' Windows: Detect suspicious network activity netstat -ano | findstr ESTABLISHED
4. Hunting for LOLBins
Attackers use living-off-the-land binaries (wmic, certutil, msiexec). Log and audit their usage:
Enable PowerShell logging Set-MpPreference -AttackSurfaceReductionRules_Ids 75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84 -AttackSurfaceReductionRules_Actions Enabled
5. Ransomware Mitigation
To prevent ransomware encryption, restrict suspicious file modifications:
Linux: Monitor filesystem changes inotifywait -m /critical/data -e modify,create,delete Windows: Enable Controlled Folder Access Set-MpPreference -EnableControlledFolderAccess Enabled
What Undercode Say:
The rise of fake software installers (Zoom, Discord, etc.) as ransomware vectors highlights the need for robust endpoint monitoring. Key takeaways:
– Detect LOLBin abuse via command-line auditing.
– Isolate suspicious processes injecting into msbuild.exe.
– Block anomalous C2 channels (Discord, YouTube, Zoom API abuse).
– Enforce application whitelisting to prevent unauthorized executables.
Final Commands for Defense:
Linux: Harden system against unauthorized execution chmod -R 750 /usr/bin/msbuild Windows: Disable script execution Set-ExecutionPolicy Restricted
Expected Output:
- Detected `msbuild.exe` spawning unusual child processes.
- Blocked C2 traffic to Discord CDN IPs.
- Alerted on `certutil` downloading payloads.
- Prevented ransomware file encryption via Controlled Folder Access.
(Note: Removed Telegram/WhatsApp links and non-cyber content.)
References:
Reported By: Jamie Williams – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
