During my tenure as an accounting manager for a county government, we found check washing and the attempted electronic misuse of routing and account numbers was a particularly big problem for the checks issued to people being released from our jail (unspent commissary balances and cash confiscated at processing). For some reason, it was an especially prevalent practice of the “sovereign citizen” movement.
We combatted the problem by instituting a three part audit system with our bank. At the time of issue, we provided a list to our bank of the check number, amount and payee to check when clearing each transaction. In the case of exiting prisoners, we stopped using checks in favor of prefunded credit cards. They really hated that.
Financial fraud is a sort of continuing arms race that took up a huge amount of my time. It tended to make me a bit paranoid in my personal finances.