You get a warning that mods used that key is not on the server:
1. place a mod in arma3 folder, example @ace3
2. join a vanilla server (with signature tests on)
3. you get the message @ace/... is not allowed because the key is not on the server
You get a "You are kicked out of the game" message:
1. move a mod pbo for example ace_main.pbo in the Arma3/addons/ folder
2. join a vanilla server (with signature tests on)
3. -> You are kicked out of the game