We have been dealing with alot of these jokers recently. They are a big pain in the ass because they buy big ads and then use iframes to try and install malware on our sites. We never allow iframes from new advertisers unless they are companies we know and trust. However sometimes they do sneak thru...
Here is a list of companies that are going around now trying to buy advertising under pseduo ad agency names and fake websites.
Hope this helps
http://industrypace.com/fake-agency-list