This is a repost of an email I sent to some of my customers in 2012.
Q. I'm getting reports from users that are getting blocked because of the pornography category. But when I check it on trustedsource.org its not pornography. What gives?
A. Check a little feature called "Do a forward DNS lookup to rate URLs"
“Do a forward DNS lookup to rate URLs” (see attached screen shot) is a cool feature in version 7 that compares the IP address of the hosting server (if the site is currently uncategorized) against known pornographic IP hosts. The idea here is that if a server is hosting a known pornographic site, then it’s a good chance that any new website could also be pornographic. Statistically speaking, this is a good indicator and for the most part works well with few errors.
However, the risk of enabling this setting is that if a server hosts non-pornographic sites, these non-pornographic sites will get the ‘pornography’ category until McAfee reclassifies them. (http://www.siteadvisor.com/userfeedback.html) to submit a reclassification ticket.
So if you are experiencing a high number of ‘false-positives’ in the pornography category, check out this setting.
Most customers leave this setting enabled and deal with the one-off false positives as they come up. Disabling this option will simply put the site into the uncategorized section and your standard rule sets for uncategorized sites will apply.