A PSN (processor serial number) is a software-readable unique serial number that Intel has stamped into its Pentium 3 microprocessor. Intel offers this as a feature that can be optionally used to provide certain network management and e-commerce benefits. Basically, it lets a program identify individual PCs.
Pentiums are not the the first processors to be shipped with software-readable serial numbers. Sun reduced instruction set computer chips have, for many years, shipped with serial numbers, and it is a commonplace for software keys for applications software to be generated with reference to the processor ID, to provide a mechanism for copyright protection. However, Intel's PSN has caused concern to privacy advocates, on grounds that it may undercut individual user efforts to maintain their anonymity, especially when using the Internet. There is a concern that Web pages could covertly acquire PSNs which, if matched with user identities disclosed through a registration process, would facilitate detailed monitoring of the use of the Internet by the individual. For example, chat rooms could use PSNs to prevent unwelcome users from posting.
Reacting to the objections, Intel announced that they would ship Pentium IIIs with the PSN function turned off. However, since the function appears to be software-configurable without need for a reboot, this assurance seems to be of little comfort.