Michael La Pilla, an iDefense "malcode" analyst, said he first spotted the attack Sunday while browsing MySpace on a Linux-based machine. When he browsed a page headed with an ad for DeckOutYourDeck.com, his browser asked him whether he wanted to open a file called exp.wmf. Microsoft released a patch in January to fix a serious security flaw in the way Windows renders WMF (Windows Metafile) images, and online criminal groups have been using the flaw to install adware, keystroke loggers and all manner of invasive software for the past seven months.
Internet Explorer users who visited a Web page containing this ad and whose IE was not equipped with the WMF patch would not get that warning. Rather, their machines would silently download a Trojan horse, a program that installs junk software in the PurityScan/ClickSpring the family of adware. This stuff bombards the user with pop-up ads and tracks their Web usage. Only a little more than half of the anti-virus programs used at anti-virus testing service AV-Test.org flagged the various programs that the Trojan tried to download as malicious or suspicious.
Using software that captures and analyzes Web traffic, La Pilla found that the installation program contacted a Web server in Russia that tracks how many times the program was installed, presumably because most of this adware is installed by third parties who get paid for each installation. The data there indicate that the adware was installed on 1.07 million computers, La Pilla said, adding that all seven of the Internet addresses contacted by the downloader Trojan appear to be inactive at this time.
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