Stack-Smashing Protector
The Stack-Smashing Protector (sometimes called SSP, formerly known as ProPolice) is an extension to the GNU Compiler Collection that helps mitigate the damage that can be done by buffer overflow based attacks. In particular, it provides stack-smashing protection.
The Stack-Smashing Protector was originally written, and is still maintained, by Hiroaki Etoh, of IBM.
So far it remains a patch external to GCC, and must be added to GCC by developers wishing to employ stack-smashing protection in their programs. At this time, only a small number of operating system developers utilize the Stack-Smashing Protector in their projects by default; OpenBSD and DragonFly BSD. Gentoo Linux also has a version of their software distribution (Hardened Gentoo) that contains the Stack-Smashing Protector patch, but as Gentoo is primarily a source based, meta-distribution, this cannot be considered "out of the box" support.