The number of software vulnerabilities fell overall in 2009, but the number of bugs in document readers and multimedia applications increased by 50 percent, according to IBM's annual X-Force Trend and Risk Report.
IBM's X-Force research and development team studies vulnerability disclosures and collects other data on Web-based attacks. In 2009, the team recorded 6,601 new vulnerabilities, which is 11 percent less than in 2008.

But IBM said the number of vulnerability disclosures for document readers, editors and multimedia applications rose by 50 percent. IBM classifies those as client-side vulnerabilities, which also include vulnerabilities affecting browsers and operating systems.

Of the five most prevalent Web site exploits, three involved PDF (Portable Document Format) files. Attackers have had much success in finding vulnerabilities in Adobe's PDF software and conduct attacks through spam campaigns and malicious Web sites.

"There's definitely a group of bad guys out there that are targeting that piece of software," said Tom Cross, IBM X-Force research manager.

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