The anti-player plugin renames any user who connects to your server with a banned name to an alternate name. It then informs them on how to change their name via the console. By default, banned names are 'Player' and 'GoDot'
Additionally, if any connected player changes their name to a banned name, it will be switched to an alternate, and it disallows names shorter than 3 characters.
The list of banned names is read from badplayernames.ini and the list of alternate names is read from newplayernames.ini. Both of these should be located in your game mod folder - e.g. cstrike.