Palo Alto Networks verifies the URL categories to which a requested site belongs. If PAN-DB determines that a URL belongs to malicious URL categories, it does not assign the site a security-focused URL category (high-risk, medium-risk, low-risk). The firewall automatically blocks sites in these categories because they pose an unacceptable level of risk for most environments. Risk levels are reserved only for URLs that have not been classified as malicious or are no longer classified as malicious due to a lack of evidence.

The following table lists the categories that PAN-DB considers malicious and blocks by default, with the exception of Private IP Addresses. Private IP addresses (and hosts) are unique to the host environment and are invisible to PAN-DB. As a result, Palo Alto Networks does not assign a risk rating to sites in this category.