The operations of the iframecash.biz gang has been covered in our blog before. Basically, they've been buying traffic from anybody who's been willing to sell it to them - then they use exploits to take over innocent surfer's computers and install trojans and spyware on them.
Now, the good news is that at least for the present, their main site www.iframecash.biz is offline. Hopefully it stays that way.