Microsoft Corp is investigating last week’s leak with the FBI, whose officials are attempting to determine which laws, if any, were broken during the incident.

News of the investigation came as reports suggested long-term Microsoft partner Mainsoft Corp was the originator of the leaked code.

Approximately 200MB of Windows 2000 and 200MB of Windows NT code consisting of shared systems libraries used when porting applications to non-Windows platforms, was released.

Mainsoft is an application migration specialist, who since 1994, has partnered with Microsoft in porting Internet Explorer, Outlook and Media Player to Unix.

Mainsoft chairman Mike Gullard pledged full cooperation with Microsoft and the authorities during their investigation. We recognize the gravity of the situation, Gullard said in a statement.

Microsoft would not confirm of deny reports Mainsoft was believed responsible or elaborate on whether the company is under investigation.

Neither would Microsoft comment on whether it is reviewing the system through which it releases source code, as a result of last week’s incident. Code is currently released to a wide range of partners, universities, governments and companies.

The incident, though, will prove a public relations disaster for Microsoft, even though the code in question is believed relatively harmless. A small proportion of code, approximately one percent of Windows 2000 plus some old Windows NT files, was released.

The code was also missing key security and network APIs, according to one expert.

However, Neel Mehta, research engineer for Internet Security Systems Inc’s XForce, said there was greatest cause for concern over the release of Microsoft’s Intellectual Property (IP) to unwanted third parties.

Despite its age, the code is likely to exist in Microsoft’s latest operating systems, Windows XP and Windows Sever 2003, and its availability means competitors not normally privy to Microsoft’s crown jewels can get a peek inside Windows.

It may enable competitors to get a better view of the underlying operating system, Mehta said.

This article is based on material originally published by ComputerWire