Microsoft has confirmed that some of the secret code underlying its Windows NT and Windows 2000 operating systems has been leaked on the internet. The company played down any potential security concerns the leak might cause.

Incomplete portions of Windows NT and Windows 2000 source code were "illegally made available on the internet," Microsoft spokesman Tom Pilla said.
Microsoft has no information on the source of the leak and has called in the FBI.

There is no indication that the leak was the result of any breach of the Microsoft corporate network or the company's internal security, according to Pilla. Also, "at this point in time there is no known impact to customers," he said.

Source code is pre-compiled code in the form of readable lines of text, usually with comments. It can be compiled into code that can run but can't be read. The Windows code on users' PCs is all compiled code.

A breach of the Windows source code - a mix of assembler, C and C++ code - could expose users to an increase in cyberattacks because it would make it easier for hackers to find holes in the operating systems that they can exploit.

It would also mean that Microsoft's closely guarded intellectual property is now out in the open, according to Joe Wilcox, a US based Jupiter Research senior analyst.

Those who say they have downloaded the source code claim to have a 200MB compressed file that expands into roughly 600MB of code.

Microsoft officials told industry analysts that this is roughly correct and that it represents about 15 percent of Windows source code.

Jupiter Research's Wilcox said a much greater percentage of the Windows code may have leaked. "It was my understanding that Windows 2000 was about 35 million lines of code." People who have seen the leaked code say it contains about 13.5 million lines.

The code leak could lead to a host of new attacks on systems running Windows 2000 and Windows NT, warned Thor Larholm, a senior security researcher at California-based PivX Solutions LLC.

"Depending on what particular code was leaked I would say this has a lot of potential for new security vulnerabilities. The next weeks to come will confirm whether we see a rise in exploits," he said.

Windows 2000 and Windows NT are older Microsoft products but are still widely used. The products also formed the basis of the current Windows XP operating system.

This is not the first time that Microsoft has faced a leak of its source code. In 2000, it confirmed that outsiders had accessed some of the code underlying a version of Windows as well as Office.