The Infected Host security category is an optional security block that will cause increased domain false positives. Infected Hosts are otherwise normal domains where an infected file has been uploaded at some point in the relatively recent past to at least one URL within that domain. This is common for large sites with large amounts of user generated content. Still, such domains may have several thousand URLs, but even if one has been infected, the entire domain will be marked. The odds of catching infection from such sites is very low as most of these domain owners will quickly resolve the problem URL before our category engines can update to reflect safe. In the meantime, users visiting harmless URLs of these marked domains will be blocked.
For this reason, the Infected Host category is considered optional and is to be managed with care.