PCI-compliant networks often contain checks for credit card numbers being sent in plaintext over the network. Problem with that is that credit card numbers are computed according to a formula, and it's really easy to generate a bunch of fake 16-digit numbers that will pass the check. So if you want to troll your security team, generate a CSV with a stack of credit card numbers and drop it in a few places on a server. Even better, set up a script to send it over the network somewhere. Then wait for the scan.

Piece on check digits, for reference: http://www.datagenetics.com/blog/july42013/index.html