Paranoia is a small addon which keeps a constant lookout for enemy players. It does this by parsing certain chat messages and if it detects an enemy player, it will play a sound and show the enemy player in a small window, together with its class and level (if this information can be gathered). You can then click the player directly to target him/her.

You can move the window around by left clicking into it and dragging it (NOT the title). You can bring up the config menu by right clicking into the window or by typing "/paranoia".