I recently helped get rid of some malware from a site. Bad stuff was inserted into every page.
In addition to the crap in the site’s 16 pages there were over five thousand extra pages with malware. Apparently it was there for quite a while.
We deleted the bad stuff and secured the site and when I was done the owner asked me how to know if this kind of thing ever happens again. Coincidentally Google has just come out with a free service to help. Follow changes to any website is a very cool service that notifies you when a website page changes. Not just a blog, but any page.
Everyone with a website should check this out.