A senior Microsoft Corp. executive told a federal court last week that sharing information with competitors could damage national security and even threaten the U.S. war effort in Afghanistan. He later acknowledged that some Microsoft code was so flawed it could not be safely disclosed.

During his second day on the stand, Allchin conceded that Microsoft has already identified at least one protocol and two APIs that it plans to withhold from public disclosure under the security carve-out.

The protocol, which is part of Message Queuing, contains a coding mistake that would threaten the security of enterprise systems using it if it were disclosed, Allchin said.

When Kevin Hodges, attorney for the dissenting states, asked him how many APIs would be exempt, Allchin said he did not know the exact number, but it would include APIs that deal with anti-piracy and digital rights management. Microsoft has already identified APIs involved with Windows File Protection that would be withheld, he said.

When pressed for further details, Allchin said he did not want to offer specifics because Microsoft is trying to work on its reputation regarding security. "The fact that I even mentioned the Message Queuing thing bothers me," he said.