Security Experts:, Other High-Profile Sites Hit by Malvertising Attack

A major online advertising company has been serving malicious ads on several high-profile websites, Fox-IT reported on Wednesday.

According to researchers, the malicious advertising (malvertising) campaign has affected popular sites such as,,,,,, and

The websites themselves have not been compromised, but some of the ads they had displayed between August 19 and August 22 were designed to redirect visitors to malicious websites. Fox-IT saw a higher than usual number of infections during this period, which isn't surprising considering that the infection process takes place quietly in the background, without the victim having to click on the malicious ad.

In this particular attack, users were redirected to a website hosting the Angler exploit kit, which pushes a piece of malware onto computers by exploiting vulnerabilities in software like Flash Player, Microsoft Silverlight and Java. The threat distributed in this campaign was Rerdom, which Fox-IT initially mistook for Asprox because the two pieces of malware are affiliated.

Researchers pointed out that such attacks are difficult to track because of retargeting, a form of targeted advertising in which companies serve ads based on the websites visited previously by the user. Ad providers keep track of users' actions with the aid of tracking data, such as cookies.

"We have seen examples where the website that helped with the ad redirect to infect a user had no idea it was helping the delivery of certain content for a certain ad provider," Fox-IT researcher Yonathan Klijnsma said in a blog post.

The advertiser whose services were abused in this campaign is AppNexus, a New York City-based firm that specializes in real-time online advertising. The company took steps to remediate this problem after being notified by Fox-IT, but this isn't the first time it was involved in a malvertising campaign. Klijnsma noted that the same company's services were abused two months ago to serve malicious ads via Skype.

Malvertising campaigns can be highly efficient in spreading malware. In June, Malwarebytes spotted an operation leveraging Flash-based ads to deliver malware with the aid of the RIG exploit kit. In July, Symantec warned that cybercriminals were using malicious advertisements served through the video sharing website Dailymotion to target internauts in the United States and Europe.

"Malvertising affects all Internet users and is a disruptor for the Internet economy. It underscores the sophistication of the modern cybercriminal economy in terms of the division of labor, cooperation, and specialization across the attack chain," Marc Solomon, Cisco's VP of Security Marketing, wrote earlier this month in a SecurityWeek column. "It also underscores the need for an approach to security that addresses the full attack continuum. With ongoing visibility and control, and intelligent and continuous updates, security professionals can take action to stop the inevitable outbreak."


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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.