Richard Stallman: Can you trust your computer?

Proprietary software means, fundamentally, that you don't control what it does; you can't study the source code, or change it. It's not surprising that clever businessmen find ways to use their control to put you at a disadvantage. Microsoft has done this several times: one version of Windows was designed to report to Microsoft all the software on your hard disk; a recent "security" upgrade in Windows Media Player required users to agree to new restrictions. But Microsoft is not alone: the KaZaa music-sharing software is designed so that KaZaa's business partner can rent out the use of your computer to their clients. These malicious features are often secret, but even once you know about them it is hard to remove them, since you don't have the source code.