We used to do the same thing back in the 1990s, but this wasn't a joke. After someone was caught with some CP on-prem we installed proxy and monitoring software, I wrote the log extraction scripts that gathered, sifted and ranked the internet proxy data and sent the weekly reports to the Sec team. We didn't tell anyone we were doing it but some people found out the hard way that surfing on the salubrious areas of the internet on work kit will get you a warning and sometimes marched offsite.
I even had to write a testing util that had a list of 50 bad sites it would randomly pick out to test that the filter was working. Let's just say that the scum moved onto the internet very early, scanning for rascist, gambling and sex sites back in the 1990s when there were almost no guidelines meant the second you got "on site" you got the full blast of the mental sewage that some people carry around in their heads.