[Big Al]

I am not a tech and so would not presume to advise on that side of things, but have you considered why some one would go to the trouble of hacking you?

Have you alienated some one recently? A pissed off ex or current member could do many things to a site.

Improving security may not be as effective, if the hacker is motivated by past grievances.

And this issue, if there, may need to be resolved in a reasonable manner as well.

The defacing of a site has to have a reason.
You ask if there is anything else you could do.
I would consider it wise to check if you have upset anyone unjustly recently.