Looks like a lot of sites running phpBB 2.x have been getting hit by the Perl.Santy worm. Symantec Security Response says,
Perl.Santy is a worm written in Perl script that attempts to spread to Web servers running versions of the phpBB 2.x… .
The worm, deletes certain types of files, including
.asp .jsp .php, and puts the following on the site that was compromised:
This site is defaced!!!
NeverEverNoSanity WebWorm generation 11.