The OP knew there was a lawsuit against him/her and did nothing. Except for a few rare circumstances, garnishments just don't happen for no reason. The state of Illinois did not garnish the bank account, they gave the authority through their court system. Chien is incorrect in his assumptions, a lein has been placed on the account and any subsequent deposits will be held till the judgment is satisfied.
What the OP needs to do is find out who sued and find out if the suit was properly served. You can go to the courthouse that granted the judgment and find out. Come back when you have that information.
If you feel my answer is rude, mean, snarky or in anyway not to your liking, I did my job. You don't need to tell me.
No private messages, I do not reply to them.