1. WordPress Firewall 2 – works good by blocking a lot of hackers attacs. When this plugin is active you can’t update wordpress files manually even when your IP is in white list. So if you need to do some changes in wordpress files deactive temporary this plugin, do the changes and active it again.
2. TimThumb Vulnerability Scanner – scan all worpress files and find those should be updated to new version.
3. W3 Total Cache – allows to avoid CPU overload.