You can also try looking at /etc/fstab and seeing if you have lines for /var and /tmp .....
if you do you can change the options to include "nosuid" and "noexec" separated by commas then remounting with "mount /var -oremount" and "mount /tmp -oremount".

If you dont have lines for /var and /tmp you should investigate how to build a secure linux box.. the idea behind using different partitions is that you can mount them with different options as above.

I reccomend :-
http://www.tldp.org/LDP/solrhe/Secur...ution-v2.0.pdf

even though it is designed for Redhat, you can apply the principles to any linux OS.

Cheers