Note: You are currently viewing documentation for Moodle 1.9. Up-to-date documentation for the latest stable version is available here: suhosin.
Suhosin is an advanced protection system for PHP installations. It was designed to protect servers and users from known and unknown flaws in PHP applications and the PHP core. Suhosin comes in two independent parts, that can be used separately or in combination. The first part is a small patch against the PHP core, that implements a few low-level protections against bufferoverflows or format string vulnerabilities and the second part is a powerful PHP extension that implements all the other protections.
For more information about suhosin, please see: http://www.hardened-php.net/suhosin/
Some moodle bug tracker tickets and moodle discussions also mentioned about suhosin: