Typical infection chain:
Execution: Attacker accesses http://target.com/b374k.php and provides a password (if set).
Post-Exploitation:
If your antivirus or file integrity monitor flags b374k.php on your server, do not panic. But do not simply delete it. Follow this forensic process. b374k.php
Check your web server access logs (/var/log/apache2/access.log or /var/log/nginx/access.log). Search for the filename:
grep "b374k.php" access.log
grep "wp-verify.php" access.log
Look for the first GET request to that file. The source IP address is the attacker’s (though likely a VPN/proxy). Also look for POST requests after the GET – that shows what commands they ran.
As of 2025, b374k.php is over a decade old. Why hasn't it died? The answer is simple: unpatched legacy systems. There are millions of servers running PHP 5.6 (end-of-life in 2018) with outdated WordPress plugins. For attackers, b374k is a reliable, well-documented, "set it and forget it" tool. Typical infection chain:
Furthermore, modern ransomware gangs (e.g., LockBit, BlackCat affiliates) have incorporated b374k into their initial access toolkits. They use it not as the final payload, but as a dropper—a simple tool to upload the more sophisticated Cobalt Strike beacon or ransomware binary.
We are also seeing the rise of AI-generated variants. Attackers feed the b374k source code into ChatGPT or CodeLlama and ask it to "rewrite this without changing functionality, but using different variable names." This easily defeats signature-based antivirus.
The b374k.php script is a notorious PHP backdoor that allows an attacker to execute commands on a server, essentially providing a remote shell. This tool is often used to compromise web servers and can lead to significant security breaches. The purpose of this paper is to explore the functionality, implications, and detection methods of the b374k.php backdoor. Execution: Attacker accesses http://target
The file must be deleted immediately. However, simply removing the file may not be enough. Administrators must investigate how the file was uploaded to prevent recurrence.
Using the b374k port scanner, the attacker probes internal IP ranges (e.g., 10.0.0.1 to 10.0.0.254). If they find port 3306 (MySQL) or 22 (SSH) open on an internal server, they use the stolen credentials to pivot.
| Attribute | Details |
| :--- | :--- |
| Filename | b374k.php (can be renamed to any .php, .php5, .phtml, etc.) |
| Typical Size | 10KB – 200KB (depending on version and obfuscation) |
| File Hash (Example) | 7a3e7f9b8c2d1a5e6f4g8h2i3j4k5l6m (varies by version) |
| First Seen | ~2012 (still actively used in 2025) |