Watch out for this nasty little browser hijacker.
I came across it on several websites purporting to offer free downloads of various texts, and prerequisite to acquiring such, it redirected to a number of sites requiring personal information, including a credit card number (ostensibly to validate address).
It's been out there a while and can do some bad things within OS X.
Wikipedia has an entry for it (http://en.wikipedia.org/wiki/Genieo
) which is worth a boo.