How to prevent the site from virus?

[now_i_m_here]

How can i prevent my site from virus?

Also how to remove it if they already infected me ?

Thanx in advance.

[davehivelocity]

Well sites do not get viruses are you talking about a shell? rookit maybe?

If you install rootkit hunter on your server it will help find shells and root kits and eliminate them. Also you can use php and edit the permissions and disable functions that allow such shells to run but to not disable too many functions or some php scripts that are poorly built will fail to run.