Much like the lovable pooch who will alert you when strangers wander around the vicinity of your home, K9 Web Protection will bark at kids who try to use the family computer for evil instead of for good.

It's a Web-based filter that also prevents against 'phishing' scams and it's aimed primarily at parents who want to keep their kids safe while they use the family computer unsupervised. Best of all, it's free!

K9 can be downloaded from here, and requires a valid e-mail address so that an activation code can be sent. One activation code is valid for one computer only and once installed a shortcut will be placed on the Desktop, which will launch the Web-based K9 interface. During the installation procedure, an administrator password must be entered, and this password is required to access K9's Web configuration interface, as well as override blocked content. It's also the password that will be needed to uninstall the program.

From the Web configuration interface, administrators can view, in detail, all the sites that have been visited; green sites are ones that have been allowed, while red sites have been blocked. A blocked site is met with a conspicuous K9 Web page, which gives the average user no chance of getting around it; only the administrator's password can bypass the block. You can even set an audible notification when attempts are made to access blocked content – yes, it's a recording of a barking dog!

Administrators can modify a block operation to include a domain, all pages within a domain or all content within the category of the domain (for example, Personals/Dating if you are visiting RSVP.com). These modifications can be made on-the-fly when the site is blocked, either permanently, or only for the next 15 minutes. Indeed, perhaps the best way to tune K9 is to visit all the sites that you want to allow access to and unblock them permanently when the K9 alert page is presented. Or, you can change the broad levels of protection.

By default, K9 will allow access only to the most safely categorised sites – news and government sites, for example – while hindering access to social networking and streaming sites (strangely, Youtube was blocked, but Google Video wasn't), as well as dating and porn sites, pretty much anything that features nudity and torrent sites. Many bomb making sites, for example, can still be viewed; however, this will be the case for any undesirable content that's located on as yet un-flagged servers and found through Google. Apart from the default setting, you can select either more aggressive or more lenient levels of protection.

Using the Web interface, you can add any sites which you think should be blocked, and by the same token, unblocked sites which don't pose a threat. In fact, K9 is highly customisable in this regard, and can even set blocks using keywords, which is very effective at blocking Web searches of undesirable terms. Furthermore, Web access can be entirely blocked according to the time of day, and this is very easy to implement, simply by graphing in a visual manner the time of day and the days of the week you want to block.

As for performance, K9 didn't hinder our Web browsing experience at all. We didn't notice any sluggishness as Web sites were checked by K9's servers in real-time and because K9 is such a small program (it'll consume less than 900KB of disk space and 4MB of memory), even the slowest of computers can run it effectively. If you want to protect your kids from the worrisome Web, K9 is well worth the download.