Step-by-Step Guide to Detecting the DEEP#DOOR Python Backdoor

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<h2>Introduction</h2><p>The DEEP#DOOR Python backdoor is a sophisticated threat that uses tunneling services to steal browser and cloud credentials from compromised systems. This guide provides a step-by-step approach for security professionals to detect, analyze, and mitigate this stealthy framework. By following these steps, you can identify suspicious activity, block exfiltration channels, and remove persistent access mechanisms.</p><figure style="margin:20px 0"><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnv1KtLLlZSnm9a16bN-o_szrBiAIN_QljTfe09K4RzFxSqhFADtuXmRzOPZ_Poazif-VadFAnRnboCWX5yZtc5JntGopn5Fy6T1X2BexXelFOxYtEA7qULoTCkAMwEybLf42JJ_yGjSPf_T-tjYvbqxscVgZ6OyL65yKcTjC0KQL48pgYLZUmLjxfBBhd/s1600/malware-data.jpg" alt="Step-by-Step Guide to Detecting the DEEP#DOOR Python Backdoor" style="width:100%;height:auto;border-radius:8px" loading="lazy"><figcaption style="font-size:12px;color:#666;margin-top:5px">Source: feeds.feedburner.com</figcaption></figure><h2>What You Need</h2><ul><li>Access to compromised endpoints (or logs) with suspicious activity</li><li>Windows Event Viewer or similar log analysis tool</li><li>Process monitoring tool (e.g., Process Monitor, Sysmon)</li><li>File integrity checker (e.g., PowerShell Get-FileHash)</li><li>Network traffic analyzer (e.g., Wireshark, tcpdump)</li><li>Python analysis environment (optional for script code review)</li><li>Threat intelligence feeds for tunneling service domains</li><li>Antivirus or EDR solution with real-time protection</li></ul><h2>Step-by-Step Detection and Mitigation</h2><ol><li><strong>Step 1: Identify Initial Infection Vector</strong><p>The intrusion chain typically begins with execution of a batch script named <strong>install_obf.bat</strong>. This script disables Windows security controls (e.g., Windows Defender, firewall) and extracts the Python backdoor payload. Look for this filename in file systems, scheduled tasks, or startup registry keys. Use <strong>PowerShell</strong> to search for the script: <code>Get-ChildItem -Path C:\ -Recurse -Filter 'install_obf.bat' -ErrorAction SilentlyContinue</code>. Check recent file events for modifications.</p></li><li><strong>Step 2: Analyze the Batch Script for Deobfuscation</strong><p>The script dynamically extracts the backdoor. Open <code>install_obf.bat</code> in a text editor and examine its contents. It likely contains encoded or obfuscated commands that decode and run a Python script. Log the decoded payload location—often a hidden directory like <code>%APPDATA%\Microsoft\</code> or <code>%TEMP%\</code>. Document all extraction steps to understand the persistence mechanism.</p></li><li><strong>Step 3: Locate the Python Backdoor Files</strong><p>After extraction, a Python script (e.g., <code>svchost.py</code> or <code>chrome_updater.py</code>) masquerades as a legitimate process. Search for Python files that are not part of official Python installations. Use file hashing to compare with known samples from threat intelligence. Also, look for accompanying configuration files (<code>.config</code>, <code>.json</code>) that may contain C2 server addresses.</p></li><li><strong>Step 4: Examine Persistence Mechanisms</strong><p>DEEP#DOOR establishes persistence via scheduled tasks or registry run keys. Check <strong>Task Scheduler</strong> for tasks named after the backdoor (<em>e.g.,</em> “WindowsUpdate” or “OneDriveSync”). Verify registry hives: <code>HKLM\Software\Microsoft\Windows\CurrentVersion\Run</code> and <code>HKCU\...\Run</code>. Remove any entries pointing to the malicious Python script.</p></li><li><strong>Step 5: Monitor for Tunneling Service Connections</strong><p>The backdoor uses third-party tunneling services (like ngrok, LocalTunnel, or serveo) to bypass network restrictions. Analyze outbound connections to known tunneling domain patterns: <code>*.ngrok.io</code>, <code>*.loca.lt</code>, <code>*.serveo.net</code>. Use network monitoring tools to alert on these connections. Correlate with process names of the backdoor (e.g., <code>python.exe</code> or <code>svchost.exe</code> spawned from non-standard locations).</p><figure style="margin:20px 0"><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyqUz0-ifa8jE9rCzud3wzxmhcuzTp1VOWFEvGMoZXDYfaB_4459fPyvyQw7wvAnzjzDL09PkyJM83QGheO69fC3esg1WA7WnJ89i_t_q3K8DxYmgV__QujU8RWRnCK4MpbKqu8nwuMFfLaiRVHy_ov7IZ16hoKI3rIu-5BcISmqXPjlQU7N0sa4lWI-n-/s728-e100/wiz-d.png" alt="Step-by-Step Guide to Detecting the DEEP#DOOR Python Backdoor" style="width:100%;height:auto;border-radius:8px" loading="lazy"><figcaption style="font-size:12px;color:#666;margin-top:5px">Source: feeds.feedburner.com</figcaption></figure></li><li><strong>Step 6: Check for Credential Harvesting Activity</strong><p>The backdoor targets browser-stored credentials, cloud service tokens, and saved passwords. Inspect browser profile directories (e.g., <code>%LOCALAPPDATA%\Google\Chrome\User Data\Default\Login Data</code>) for unusual file access times. Use Sysmon Event ID 11 (FileCreate) to track modifications. Also, look for PowerShell commands that decrypt browser data (e.g., <code>DPAPI</code> calls) or access cloud configuration files like <code>.aws/credentials</code> or <code>~/.azure/accessTokens.json</code>.</p></li><li><strong>Step 7: Isolate and Remove the Backdoor</strong><li>Once confirmed, isolate the affected machine from the network to prevent data exfiltration. Kill processes associated with the Python backdoor using <code>taskkill /F /PID [PID]</code>. Delete the extracted files and any scheduled tasks. Run a full antivirus scan and rotate all credentials stored on the device. Consider reimaging the system if persistence is deeply embedded.</li></li><li><strong>Step 8: Verify Removal and Conduct Post-Mortem</strong><li>After cleanup, monitor the system for 48 hours for any recurrent indicators. Check event logs for backdoor-related IDs (e.g., process creation events). Update detection rules in your SIEM to block similar patterns. Document the incident and share indicators of compromise (IOCs) with relevant stakeholders.</li></li></ol><h2>Tips</h2><ul><li>Always test detection steps in a sandbox environment before deploying to production.</li><li>Use threat intelligence sources to update blocks for tunneling service domains regularly.</li><li>Enable <strong>Windows Event Logging</strong> for process creation (Event ID 4688) and command line auditing to capture batch script execution.</li><li>Educate users about phishing emails that may deliver <code>install_obf.bat</code> as an attachment.</li><li>Implement application whitelisting to prevent unsigned Python scripts from running.</li><li>If you suspect credential theft, immediately reset passwords and revoke cloud API keys.</li></ul>