Security researchers have uncovered a new wave of malicious advertisements which has been attacking users this week.
Security firm ScanSafe said that the attacks had been serving up exploits for a three day period from September 19 to 21. The company said that the infected banners were displayed on a number of prominent web sites including the Drudge Report and Lyrics.com.
According to ScanSafe, the banner ads had been embedded with code which referenced third-party attack sites. The attack sites then attempted to exploit both PDF and ActiveX browser vulnerabilities to install a trjoan downloader which in turn summoned malware to log search data and redirect web traffic.
The company said that the attacks were not unique and that similar cases have been spotted since July. The company noted, however, that the malware used for the PDF attacks was particularly hard for security software to detect.
Use of malicious ad banners or 'malvertising' has become an increasingly high-profile topic lately.
Malware writers often conduct the attacks by embedding seemingly legitimate banner ads with small amounts of code that reference remote attack sites. The result is an advertisement which can leave otherwise legitimate sites unknowingly putting users at risk for infection.
Earlier this week, Microsoft said that it would be suing several companies which it believed to be behind numerous malvertising attacks on its advertising networks.