PHP Web Shell Dor

The PHP web shell ‘Dor’ contains the functionality to upload files. This can be useful to attackers who want to upload further pieces of malware to the vulnerable server. This shell has been obfuscated with several PHP functions, such as str_rot13, gzinflate, and base64_decode. The sample can be uploaded via an upload mechanism or vulnerability in the server.

Exploitation

Stages

1. An attacker uploads a PHP web shell to the vulnerable server via an upload mechanism or vulnerability.
2. The server responds indicating a successful upload.
3. The attacker acts upon objectives by utilizing the shell’s functionality.

Prerequisites

The attacker must be able to inject the malicious code onto the web server through another vulnerability or exploit.

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

The attacker must have exploited some other entry vector to allow the malicious files to become resident on the victim machine.