Setup your firewall to block sites with dynamic WAN IPs.

In some cases you would like to block Facebook, Spotify, Twitter, Youtube etc. in your company
The problem is that their WAN ip changes constantly.
You are able to find some information on the internet informing you of the ranges that the sites are using, but it is not always accurate.

You will find the current WAN IPs here as well as the IP that has been used before. The list for each site is updated every minute.
You can also down a complete log.