Three wordpress sites now blank simultaneously!

Hi,

this morning I was greeted to three of our wp sites (all on the same server) being blank.
I checked the ftp and there were modified versions of index.php for today’s date, but they looked wordpress legit. There were also modified fix_wp-atom.php today but I don’t know what that’s for.

Anyway, I tried the usual fixes: renaming the plugins and themes folders temporarily to get into the wp-admin, and that didn’t work.

Help! They’re all blank!

sexdrugsandjunecleaver.com
dinglecomic.com
glassurchin.com