Running a business
My favourite wasn't porn but printing. We did a traffic analysis on a certain government department as part of planning a printer upgrade. Strangely, a number of print jobs had names like "Invoice xxx" but the work of the department didn't involve invoicing.
Sure enough, a soon to be ex member of staff was found to be running a business at work down to printing invoices on HMGs printers and sending them out via the print room. And this had not been noticed for quite a while.
As a result, no example of government incompetence can possibly surprise me any more.