A security company known for paying bounties on bugs will launch a new program next week that will pay researchers $10,000 for finding Windows vulnerabilities that Microsoft classifies as "Critical."

The new reward is an addition to iDefense's controversial Vulnerability Contributor Program (VCP), which launched in 2005. "We want to get people excited [about VCP]," said Adam Greene, the assistant director of iDefense Labs. "And we want to encourage researchers to focus on things important to our clients."

Windows vulnerabilities was an obvious pick, added Greene, because "so many of our clients use [Windows]."

The $10,000 research reward comes with a few strings. The offer ends March 31, said Greene, and it must be submitted exclusively to iDefense. If Microsoft eventually classifies it as a "Critical" fix -- the Redmond, Wash.-based developer uses a four-step rating system to rank patches, with Critical at the top of the chart -- iDefense will pay out the $10,000, which is above and beyond its usual VCP payouts. Although iDefense doesn't publish it usual reward rate structure, it paid out nearly $40,000 in its first three months.

Each quarter, iDefense will change the rules of the $10,000 bonus. "We haven't settled on next quarter's," admitted Greene. "But rather than a specific vendor, we're talking about targeting a certain class of vulnerability or class of product. Maybe Web browsers or e-mail."

"It's important to change it up a bit to keep people interested," he added.

A few other companies trade cash for vulnerabilities. TippingPoint, part of 3Com, has a similar program, dubbed Zero Day Initiative, while Mozilla pays $500 for bugs in its open-source software.