Kigen's Anti-Cheat

I haven't played CSS in about 5 years and i come back to see I cant connect to my old clan server cause i am kac banned what does this mean?

It means that the Steam account you are using is banned from the KAC protected server you are trying to play on.
I really don't have enough information in ...

I haven't played CSS in about 5 years and i come back to see I cant connect to my old clan server cause i am kac banned what does this mean?