Microsoft Details Cookie-Controlled PHP Web Shells Persisting via Cron on Linux Servers
Apr 03, 2026
Linux / Server Hardening
Threat actors are increasingly using HTTP cookies as a control channel for PHP-based web shells on Linux servers and to achieve remote code execution, according to findings from the Microsoft Defender Security Research Team. "Instead of exposing command execution through URL parameters or request bodies, these web shells rely on threat actor-supplied cookie values to gate execution, pass instructions, and activate malicious functionality," the tech giant said . The approach offers added stealth as it allows malicious code to stay dormant during normal application execution and activate the web shell logic only when specific cookie values are present. This behavior, Microsoft noted, extends to web requests, scheduled tasks, and trusted background workers. The malicious activity takes advantage of the fact that cookie values are available at runtime through the $_COOKIE superglobal variable, allowing attacker-supplied inputs to be consumed with...
