First off, I'd email this guy back demanding my exact IP, remote port (my port), local port (the port on his computer), protocol, date, and time that was used to gain illegal access to his database. Second, I would check my firewall logs and compare the information.

I probably have close to 10 months of firewall logs saved on my hardrive right now (I'm trying to maintain about a steady year's worth of activity which will amount to less than 6MB's). So if and when this guy is able to provide that information, I might start finding it odd when I see no such connection was ever established from my computer (but I wouldn't mention that to Mr David Chang as this is where it would get fun).

Now, I'm sure the common user won't have a year's worth of recorded activity but I'm not the common user and it only takes one person to throw a wrench into this supposed scheme. (I'm sure I'm not the only person on the planet who records firewall logs either). After I determined this schmuck was a fraud, I'd play a little reverse social engineering and get as much information out of this guy as I could by playing dumb to his ploy. I'd then contact the appropriate people and screw this guy on as many levels as I could.

Well, that's my input on the matter. Just something off the top of my head .