Your server most likely has backdoors in it

That's right, with the credits to http://glua.team/ they released a huge mega thread of backdoors, I'd recommend searching through them if you see any addons you might have.

Also for developers, I've found a lot of vliss leaks in there, you might wanna check and see if your script files might be there.

Source https://facepunch.com/showthread.php?t=1552592

Just making this thread cause most server owners don't even know about facepunch