My client's website was recently defaced and they are seeking was to mitigate this risk. They have a dedicated server running apache and mod\_php. The website consists of three separate php applications installed in different folders (Customer portal script, wordpress and a custom database driven script). Their security audit recommended that each script be isolated so that if any of them was hacked, the other two would be safe from defacement etc. They also recommended using fast-cgi over mod\_php. Suexec was also mentioned although its not clear why this was recommended.

Can someone please confirm if this makes sense and is actually possible/feasible. If so, what would be the best way to achieve the proposed security solution?