A friend of mine was a user of a website like blackplanet.com, collegeclub.com, etc....

The kind where you chat, message, email, etc. all web based. My friend exchanged an email and converstion or 2 with an individual who now has all their email addresses, etc, and is threatening them.

They said something like "They got all their email addresses from their IP address."

These are work, personal, etc...

My theory is that this person knows my friend somehow, and is not a random person.

Is it possible to obtain that type of information from an email based on one of those sites?

"They got all their email addresses from their IP address.".. Well kind of possible, they could maybe find out their ISPs domain from an IP and figure out their email address.. If they could get their IP to begin with.

I would say your theory sounds good, but anything is possible really, if this individual they spoke to has too much time on their hands and is very smart, then they could maybe figure out a few things, but I would say they couldn't find out ALL the email addresses that person has etc..

have you got an e-mail of the person, which was send from his home-pc ?
The mail-headers tells a lot about the person (PC-Name, Ip Address at that time...)

...They got both the work Email account info and the personal Email account info. Now the only thing those two have in common is they're both connected to the internet...Can U say Trojan?

Start scanning == Now...!

its got norton corporate running..but I'll be scanning it tommorrow. all current theories are pointing to the person who already knows my friend..

I had a friend call me up last night with almost the same kind of problem, he was using Yahoo Chat and spoke to some person and not too long after that person has been harrasing him, he knows alot of my friends personal details, and he's threatening to post them on the Internet. They've come down to the same conclusion that it must be somebody who knows him somehow.