The CustomShell web shell provides attackers with the ability to execute OS commands, traverse directories, and upload files. The web shell will fall back to custom PHP shell functionality if the PHP program execution functions are not available.
- The attacker sends a multipart HTTP POST request that was generated by the web shell to the compromised server.
- The compromised server replies with HTTP 200 OK and the HTML interface for the web shell.
The attacker must have exploited some other entry vector to allow the malicious files to become resident on the victim machine.
Alert Logic Coverage
Alert Logic® has evaluated its customer base for exposure to the exploit and has developed signatures for mitigating the threat depending on the security service in place.
The Network-Based Intrusion Detection System (IDS) has been updated with the new signatures for this exploit when detected via Alert Logic Threat Manager™. If this signature is detected, an incident is generated in the Alert Logic console.
Recommendations for Mitigation
Ensure that all public internet-facing applications have the most up-to-date patches applied.