Sometimes say things like "ya'll white ass crackaz would get shot if ya came to my hood nigga" when they are really just a skinny, middle class white loser who lives with their mum in the suburbs.
For excellent examples of internet gangsters, check out Yahho chatrooms/groups/gangland room, and also YouTube.
Not to be confused with the idiots who act tough online.
When you confront them in person they will hide behind their other friends, even attempt to amend things and get closer to you through your other friends, gfs, bfs. In fact when you confront them about being an Internet Gangster.. They will shrug their shoulders, turn around, and walk away. Like a punk.