I suspect that most IT security managers would initially respond to an intrusion by turning on programs that would log the intruder's activities. To prevent re-occurance, they'd want to know the intruder's identity, method of penetration, activities, etc. Also, any form of prosecution would depend on this. (See, for example: http://www.cert.org/security-improvement/modules/m06.html .) Thus, the intruder would likely NOT KNOW immediately that his presence had been detected.) The second question, whether someone could "accidentally" intrude on someone else's computer is more speculative. In general, people don't accidentally access, much less penetrate, another computer, but it's possible, just like it's possible for a legitimate deliveryman knocking at a door to find that it swings open (because it's unlatched). Ultimately, I think that the important issues are things like motivations, damages, knowledge that it was a secure area being intruded upon, etc. Peter Hollings ********