Originally Posted by griffin
IP addresses, mainly. Of course there are limitations to using IP to match people, and there are ways to avoid detection, but every now and then someone goes out of their way to make it obvious.
Detection by IP address is not really valid. Examples:
1) if you sit behind a firewall of big corporate network with private address space and single pro-xy server for all outgoing traffic, every single person posting from that network will be seen outside as having the same IP address. The same is true for many ISPs who can not afford allocating public addresses. I used to communicate from a major ISP in Moscow, and I was behind not even the first - the second layer - of private addresses. Public addresses cost money. Private addresses are free.
2) if you are using a dialup provider, such as AOL, CompuServe or Netzero, you are likely to get different IP address every time you dial. On the other hand some people are certain to be given the address that you previously used
3) There are hundreds of freely available public pro-xy servers who can help you look like you are wherever you want to look being right now.. From France to China.
4) Some people like me could post from dozens of locations - like from home, or occasionally from work, or from friend's place, or from my supplementary dialup provider when I am on the road , or from Starbucks wireless , or from airport wireless. I am sure that if IP addresses are on your database, you can see me with dozens of different IPs. What does it tell you?