Yesterday “Iskorpitx”, successfully hacked 21,549 websites in one shot and defaced (on a secondary page) all of them with the same . This is the biggest hack in web hosting history.
The website of this hacker is
mavi1.org
My office's site was also hacked by the same hacker. It just changes the index page of a website. So the instant solution is replace your actual index file to server. I am sure that it will be solved the problem.
Thanks
Anjuman