Wordpress Security/Bug/Plugin Fix

I manage about 15 blogs. The blogs were attacked a second time again either by hacker or bug. When I go to the site all I get is a white screen. I also get a white screen when I go to wp admin. I fixed them once already and now it has happened again. The prior fix I used snapshots of a previous state and rewrote the files. I changed all passwords and used SFTP. I need to know why this is happening before I fix them again. Is it a corrupt code? Plugin? Here is an example: [login to view URL] I would like someone help get the blogs back online and secure them.