[jks]

He used to send out real cheques for $2.56 but apparently they contained codes that could be used to transfer money out of his account in excess of the sum of the cheque. Now he uses the made-up Bank of San Serriffe, which naturally understands hexadecimal.

https://www-cs-faculty.stanford.edu/~knuth/news08.html

[pests]

Routing and account numbers at the bottom of a check are semi-private and nefarious actors can abuse them. See the movie/book Catch Me If You Can about Frank Abigail.

[ozzmotik]

that's Abagnale, I believe.