There's really no good reason to open up your console for pretty much anyone to use on a public server. It's just going to cause trouble as it's done in the past and as it's done right here in this thread. Get rid of it.
Eval is a default console function.That's like saying "oh I think gameconnection::onSpawnPlayer(%this) is dumb".Obviously you mean giving access to it to super admins, but really, it depends completly on who the super admins are.If they're decent people then there's no problem.
Guessing the admin password would not give you auto admin. It would give you manual and the message would say (Password).
Make sure you haven't downloaded any private add-ons as well, you could have just as easily been backdoored.
Didn't you spread a back door before on purpose?