How can I determine, by IP address, if multiple user names are actually the same person? When local forum editors wish to suspend user rights for TOS violations they will often send a list of names and ask me to find out if those different profiles are actually the same person - and if they are then the editors want all names suspended. When IP addresses are identical - It can be assumed that the two different people are the same, correct? What if IPs are similar, but not identical?

If the IP addresses are similar but not identical you would have to consult with the Service Provider that owns them to check on the plausibility of them having been assigned to the same machine.

Even that isn't a foolproof method of determining that it was the same person, but it's probably good enough.