The Secure-Linux patch adds a few security features to the kernel which, while not a complete method of protection, will stop most of the 'cookbook' buffer overflow exploits cold. It also adds the option of restricting the use of symlinks in +t (temp) directories which fixes most tmp-race exploits as well. It can also add a little bit more privacy to the system by restricting access to parts of /proc to root so that users may not see who else is logged on or what they're doing.
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