SysAdminGear

Some exploits will try to use unix resources to download rootkits and other bad files to your system. You can deny it fixing some permissions on that resources.

Trick: Make a backup of /usr/bin, /usr/sbin, /bin, /sbin
You will be able to replace it if you detected some infected file with rkhunter or chrootkit.
Read this:
How to Install Rkhunter
How to Install Rootcheck

# chmod 700 /usr/bin/rcp
# chmod 700 /usr/bin/wget
# chmod 700 /usr/bin/lynx
# chmod 700 /usr/bin/links
# chmod 700 /usr/bin/scp
# chmod 000 /etc/httpd/proxy/
# chmod 000 /var/mail/vbox
# chmod 700 /usr/bin/mc
# chmod 700 /usr/bin/elinks
# chmod 700 /usr/bin/lwp-download
# chmod 700 /usr/bin/GET
# chmod 700 /usr/bin/curl

You can also block all *cc compilers on /usr/bin to permit only root user to use compilers:
# cd /usr/bin/
# ls -l
# chmod 700 /usr/bin/
Example:
# chmod 700 byacc
# chmod 700 cc
# chmod 700 gcc
# chmod 700 gnatgcc
# chmod 700 perlcc
# chmod 700 yacc