A malvertising attack targeted TweetMeme users today after a rogue advertiser made its way onto the website. The malicious advertisements directed user to third party websites displaying fake malware alerts with the purpose of convincing users to install scareware.

Malvertising (malicious advertising) is a type of attack where cyber crooks manage to insert rogue ads that lead users to malicious content into a legit website. The practice is commonly employed by scareware pushers to distribute their fake antivirus products.

According to StopMalvertising, a website dedicated to researching and stopping such attacks, TweetMeme users were targeted via malicious advertisements served by a rogue advertiser at y5-media.com. An investigation of the incident revealed that the threat distributed through these malvertisements was a fake antivirus called Security Threat Analysis.

The researchers explain that requests to y5-media.com bounce through two other websites before landing on the scareware domains. In order to fly under the radar the cyber crooks tried to make the attack as subtle as possible.

“Both domains perform various checks to see whether you’re a bot, a search engine, a proxy … as in those cases the redirect to the scareware will not happen,” the researchers explain. Also, if a user visits the malicious websites once, a cookie is added in his browser to prevent him from being targeted again.

The landing websites at www3.luckfind42td.in and www2.guardhere5.in, display the typical fake malware scans associated with scareware scams. When these scans are “done” the users are taken to another domain called www1.wareforyou10.in, which serves a file called packupdate107_302.exe for download. This is a program in the FakeAV family of malware, which currently has a very low AV detection rate.

Malvertisements can be very dangerous, because unlike black hat search optimization campaigns that poison search results with malicious links, they can are a lot harder to detect, and abuse the trust that users put into legit websites. Popular websites that were previously affected by similar attacks include the New York Times, Gizmodo or Digital Spy.

You can follow the editor on Twitter @lconstantin