We have a proof of someone receving a "tax" of -531 tokens who claimed it was due to the fact he bought 500 T on an external provider.
Therefore:

-Yes Nordues keeps a keen eye over cheaters.
-No, affirming that there aren't ways to cheat is false. the -500 T penalty means that that player used those "fake" 500 Ts and after he got caught, was punished.
-Meaning someone is actually able at least to intrude the servers and add tokens on an account.