Typically, most sites are hacked because of
older and exploitable software, or world-writeable permissions (777).
By checking monthly, or even bi-monthly for newer versions of the
software installed on your site, you are making it much more difficult
for a potential attacker to gain a foothold. World-writeable
permissions are rarely needed in any situation. Instead, please use 755
for executables, and 644 for all other files.