Microsoft Corp. last night confirmed that portions of the source code for two versions of its Windows operating system have leaked onto the Internet, a security breach that could give hackers important intelligence about how to exploit flaws in software run by many of the world's computers.
"Today we became aware that incomplete portions of Windows 2000 and NT 4.0 source code was illegally made available on the Internet," Microsoft spokesman Tom Pilla said. "It's illegal for third parties to post Microsoft source code and we take that activity very seriously."
Pilla said the company does not know how much of the code was compromised, but he said Microsoft believes it was not a complete version of either operating system. There was no indication of a breach in Microsoft's internal network, Pilla said. He said the FBI is investigating.
Windows 2000 and NT are widely deployed in business networks; less so on home computers.
Computer security experts said the release of Windows source code could pose a threat to Internet security, depending on what portion of the code was leaked.
A leak of any portion "could dramatically increase the probability that new zero-day vulnerabilities will be found," said Alan Paller, director of research at the SANS Institute, a security training group based in Bethesda.
"Zero day" attacks exploit a security vulnerability before or at the same time a software maker learns of the flaw.
Thor Larholm, senior security researcher at Newport Beach, Calif.-based PivX Solutions, said the Windows source code file being traded on the Internet appears to be roughly 660 megabytes in size, about one CD-ROM's worth of data. That is far short of the estimated 40 gigabytes of data that make up the entire Windows code.
But even a partial leak "is a potentially very serious problem for Microsoft," Larholm said. "Just look at the vulnerabilities that are discovered by people who didn't have access to the source code."
Howard Schmidt, former head of security at Microsoft, said he was less concerned about the security implications of the leak than its potential threat to Microsoft's intellectual property.
"From a security standpoint, this is sort of like capturing a 1956 Russian fighter jet," said Schmidt, now chief security officer at online auction giant eBay. "Everyone has been beating on Windows 2000 and NT for a long time, and any flaws that may be found have likely been fixed long ago. Frankly, I'd be more worried that someone was going to use this as a base for developing software or another operating system based on Microsoft's proprietary code."
The Redmond, Wash.-based software giant closely guards the Windows source code but does license portions of it to security researchers and more than 50 universities under its "Shared Source Initiative."
Microsoft, in a competitive strike against the rival Linux operating system, last year said it would began sharing large portions of the source code with governments around the world that want to validate the security of the software before deploying it in national defense and other sensitive areas.
Unlike open-source software like Linux, the code comprising Windows is not open for public inspection. Linux users are encouraged to participate in an open, continuous cycle of modifications and upgrades that its proponents say results in systems that are more secure and reliable than those powered by proprietary code like Windows.
Brian Krebs is a reporter for washingtonpost.com. Staff writers Mike Musgrove and Jonathan Krim contributed to this report.
