| Windows |
|A closed source operating system.|
Microsoft Windows is a widely used closed source operating system.
In August 1999 Andrew D. Fernandes of Cryptonym Corporation discovered a variable in Windows NT 4 Service Pack 5 (which had been released unstripped of its symbolic debugging data) entitled "_NSAKEY". Microsoft stated that this was "simply an unfortunate name" connected to NSA export control and denied that it was a backdoor for the NSA.