Hello
These are usually domains generated by some sort of application on one of the user's workstations that's "pinging" to see if there's a live internet connection. It could be an antivirus program, or any other application that does such checks.
We don't block these domains because they're not valid domains. This means that blocking them from our side wouldn't actually do much, and if they are legitimate domains that are malicious, they usually come in the form of DGA (domain generated algorithm) domains and we block those already on our malware side of things.
If you have any questions or concerns please create a support request.
