Websites may be blocked by Cisco Umbrella for several reasons, including:
Cisco Umbrella assigns a reputation score to every domain on the internet based on its history, who registered it, and where it is hosted. Even if a site isn't definitively "malicious," it may be blocked if it exhibits suspicious characteristics: why is cisco umbrella blocking websites
Occasionally, a safe website may be incorrectly tagged in a restricted category or flagged as a security risk. How the Blocking Process Works Websites may be blocked by Cisco Umbrella for