Originally Posted by k0nr4d

Filezilla stores all it's saved sites in an unencrypted xml file. I have a buddy who does german mainstream sites, and his computer got a virus. The virus sent out his filezilla xml file to some server and that server went in and added some iframe crap on every .html and .tpl file on all his client's servers. This happens less frequently on adult sites because the hosts in adult tend to firewall their shit, but there are other viruses and malware that log right in from your computer and do it - thus bypassing any firewall or anything.

It doesn't have to be *YOUR* computer that got virused - it could be a designer you hired, a programmer, a copywriter, an seo guy, or even a server admin who's computer was infected with soemthing and had your login data saved somewhere.