Security software is becoming more troublesome than some of the products it is supposed to be protecting, according to new figures from the Yankee Group. The number of vulnerabilities found in security applications has risen sharply for the third year in a row and now outnumbers those in all Microsoft products, according to the research firm.

In 2004, researchers uncovered 60 vulnerabilities in security software, up from 31 in 2003, according to the study. In May this year, 23 security bugs have already turned up, compared with 22 for Microsoft applications. The figures through May 2005 are up 50 percent over the same period last year, Yankee Group said. The figures were reported by Business Week.

Yankee Group's findings confirm a trend that has become increasingly visible in recent months, with vulnerability researchers and attackers both spending more effort on finding cracks in the programs intended to protect systems. As Microsoft has discovered in the past few years, the more companies rely on your products the more likely you are to be attacked.

This fact partly accounts for the increase in scrutiny of security software, with the largest vendors encountering the most bugs, according to Yankee Group. Market leader Symantec had the highest number of reported bugs last year -16 - though only two have surfaced this year so far. The number of vulnerabilities surfacing in security programs rose more than vulnerabilities in the software industry generally, according to the firm.

Several major anti-virus companies have had to patch serious security flaws in their core products in recent months, including Symantec, McAfee, Trend Micro and F-Secure.

In March, attackers released exploit code for a bug in Computer Associates security software, just two days after CA released a patch. CA was hit with a separate bug in May. Microsoft disclosed a vulnerability in its firewall software in December.