Malicious online advertising, or malvertising, involves the insertion of infected ad files into ad networks. Viewers of the the malicious ads are at risk of having their computers compromised by a drive-by-downloads or of being presented with a fake antivirus scam.
Malvertising compounds the problems of malware -- identity theft, fraud, and loss of privacy -- by damaging the brands of the publishers and ad networks that inadvertently deliver infected ads.
In early 2008, Niels Provos, a security engineer at Google, said in a blog post that about 2% of malicious Web sites were distributing malware through advertising, based on an analysis of about 2,000 known advertising networks.
The problem posed by malvertising was bad enough to prompt Google last summer to launch a search site called Anti-Malvertising.com to help its ad network partners fight malvertising. And Microsoft in September last year filed five lawsuits to halt the distribution of malicious ads through its online ad platform, Microsoft AdManager.
Dasient co-founder Neil Daswani, a former Google engineer, estimates that close to 1.3 million malicious ads are served every day. Such ads tend to persist for about a week before being removed, a result of the tendency of malware creators to release malicious ads over the weekend, when there's often no ad network staff around to field complaints or detect the infected files.
Dasient's answer to the problem, fittingly enough, is called Anti-Malvertising Solution (AMS). The service monitors ad networks for malicious files and automatically notifies ad network partners when malvertisements are detected. It provides a way to block malicious ads immediately and documents the information needed to remove them.
Daswani says that its better for publishers and ad networks to address the problem than to leave it up to Internet users, who might choose to block ads as a security measure.
"Advertising to an extent has funded the generation of content on the Web," he said. "As an industry, it would be disappointing if things got so bad that people shut off ads."