Technology that filters video content is still fairly new and, unfortunately, inaccurate.  

We are not aware of a technology or company that does a good job filtering videos on-the-fly. Most video filters give too many false positives (i.e., thinks the video is ok, but it's not) or too many false negatives (i.e., says the video is bad, but it isn't).

Today, Net Nanny will filter user comments on web pages such as YouTube.  And it will also review any text or descriptions of videos contained on a YouTube page. Net Nanny even looks at the HTML source code for the page. Based on what Net Nanny finds at that moment, the YouTube page will either load or it will be blocked.  Thus, if your child's profile for Net Nanny is set to 'block' pornography, Net Nanny takes the first stab at blocking.

Unfortunately, Net Nanny is not a video filter. Thus, video content is not considered in the Net Nanny review of the web page.

But YouTube does have a "safety mode" feature that can be enabled for the browser on your device or computer or for a YouTube user. Note: Net Nanny for Windows by default will automatically enforce YouTube's safety mode.

For other devices: to find the Safety Mode feature and enable it for the browser on the device or computer you're using, log in to YouTube (but not as the child you wish to protect; log in as a parent). Then go to Settings (upper right corner of the browser). Then go to Playback (left menu) and look at the bottom of the screen for "safety mode" and turn it "on" as well as "lock" safety mode for the browser.  Then click 'save.'  Now, log out as the parent. When a child logs in to YouTube, the browser will now be locked into 'safety mode.'

Once safety mode is enabled, YouTube will attempt to filter videos for the browser you or your child is using based on content.

In summary, if you have a safe web browser (like Net Nanny) that evaluates web page content, comments, headers, etc. coupled with "safety mode" turned on for YouTube, you've done as good a job as you can to set up parental blocks against inappropriate content on YouTube.

On the other hand, Net Nanny will allow you to "blacklist" a web page, such as www.YouTube.com, and that page will remain locked out and not accessible by anyone for any reason.

I work for Net Nanny and all opinions are my own.