A CARELESS mistake by Microsoft programmers has revealed that special access codes prepared by the US National Security Agency have been secretly built into Windows. The NSA access system is built into every version of the Windows operating system now in use, except early releases of Windows 95 (and its predecessors). The discovery comes close on the heels of the revelations earlier this year that another US software giant, Lotus, had built an NSA "help information" trapdoor into its Notes system, and that security functions on other software systems had been deliberately crippled.