The number of new software security vulnerabilities identified by security experts, hackers and others during the first eight months of this year has already exceeded the total recorded for all of 2005, according to Internet Security Systems.

Vulnerabilities through September have reached 5,300, leaping past the 5,195 discovered for all of 2005, says Gunter Ollmann, director of the X-Force research group at ISS.

"Eight hundred seventy-one were found to affect Microsoft operating systems, while 701 vulnerabilities were only found to affect Unix operating systems," Ollmann says. But many vulnerabilities cross platform boundaries to affect them all, including Linux. About 3,219 vulnerabilities fall into that realm, Ollmann notes. "So the volume seems to be Linux-based because there are so many versions of Linux," he says.

ISS ranks vulnerabilities as critical, high, medium and low. Of the 5,300 vulnerabilities recorded for 2006 so far, 0.4 percent were deemed critical (could be used to form a prolific automated worm); 16.6 percent were deemed high (could be exploited to gain control of the host running the software); 63 percent were medium (could be used to access files or escalate privileges); and 20 percent were low (vulnerabilities that leak information or would allow a denial-of-service attack).

The biggest single classes of vulnerabilities in 2006 so far, according to ISS, would allow cross-site scripting (14.5 percent), SQL injection (10.9 percent); buffer overflows (10.8 percent) and Web directory path traversal (3 percent).

Of the 5,300 vulnerabilities identified during 2006 so far, 87.6 percent could be exploited remotely; 10.8 percent could be exploited from the local host only; and 1.6 percent could be exploited remotely and local.

The only good news, according to ISS, is that 2006 critical and high risk vulnerabilities have decreased 8 percent from 2005, when they accounted for 28 percent.

A calendar of the most vulnerable application vendors each month through August is as follows:

January: Oracle (89); Microsoft (12); BEA Systems (12); IBM Lotus (11); Apple (10)

February: Microsoft (29); Linux kernel (14); Mozilla (12); IBM (11); myBB (9)

March: Microsoft (18); Linux kernel (14); Mac OS X (14); Mantis (6); HP (6)

April: Oracle (36); Ethereal (27); Mozilla (26); Microsoft (20); Apple (9)

May: Apple (32); Microsoft (13); BEA (11); Linux kernel (10); IBM (9)

June: Microsoft (27); Mozilla (13); Cisco (10); Particle Soft (9); MailEnable (7)

July: Oracle (65); Microsoft (55); Mozilla (14); Cisco (9); OpenCMS (9)

August: Microsoft (32); Informix (16); Mac OS (16); IBM (8); JetBox CMS (8)

ISS is assembling data on September, and Ollmann predicts there will be a surge of more software vulnerabilities before the end of 2006. "The last quarter is often the busiest," he notes. Ollmann adds that the biggest vulnerability discoverer over the last 10 years is someone who goes by the name "r0t," with 501 vulnerabilities -- but only one classified as high risk.