Enterprises invest in technology from vendors to help filter out bad Web sites from touching their networks, but the same technology, at least some of it, can be had by consumers for free.

And for networking vendor Blue Coat (NASDAQ: BCSI), the strategy is paying off. While Blue Coat is best known for Web filtering for enterprise customers, its free, K9 consumer product is making waves, having hit the million-download milestone.

It might not be surprising that K9 is seeing a great deal of traction, considering it uses the same filtering technology as found in Blue Coat's widely deployed enterprise edition.

The application's success also may not be surprising considering that the need for Web filtering has become increasingly important lately. In addition to malware sites, legitimate sites are also being targeted for malware distribution, making it even more critical that users have proactive Web filtering.

"We've had a million downloads for K9, so there is quite a large user community using K9 today to protect their computers from malware, and it's used a lot as a parental control tool to keep kids off sites that parents don't approve of," Mikko Valimaki, chief scientist at Blue Coat, told InternetNews.com.

With such demand, why give away the technology?

To Blue Coat, the idea behind K9 is twofold. The company has an altruistic goal of protecting users, but it also uses the information it learns from consumers and the sites they visit to protect paying enterprise customers.

"We decided that we're not in the consumer business -- Blue Coat sells to large organizations and that's where our focus is," Valimaki said. "But we figured it was important for us to be part of the community and have visibility into what is going on the Web."

In so doing, Valimaki argued that Blue Coat is part of the broader solution to help combat malware sites. Specifically, it can glean additional visibility from consumers that enables it to better identify and fight malware sites.

That makes for a compelling reason for consumers to download K9, which in turn helps Blue Coat -- even though it's essentially giving consumers free access to the same anti-malware cloud service that powers its enterprise offering.

"In effect, the free K9 home product is using the same knowledge and intelligence in the cloud as our corporate solution, the Blue Coat Web filter," Valimaki said.

K9 relies on Blue Coat's cloud-based WebPulse service to filter site requests based on categories -- like gambling or pornography -- as well as malware site blocking. WebPulse is also used by Blue Coat's ProxySG appliance, which also provides Web acceleration capabilities for businesses. Valimaki claimed that K9 users get the same speed of service that enterprise gets and Blue Coat does not throttle the service.

Valimaki explained that Blue Coat has four datacenters worldwide that receive K9 requests. When a user hits a new site, K9 triggers a lookup on the WebPulse cloud service about the site's category, enabling K9 to make a policy decision about whether to block the site.

If a site request is not in the existing WebPulse database, Blue Coat's technology makes a decision based on what Valimaki described as the site's "reputation."

"Consider you have a dot-com domain being a referrer to a domain in China, and it was just recently brought online, and it's hosted on the same IP address that has previously pushed malware," Valimaki explained. "We can fairly easily determine if something is suspicious just based on the request."

K9 also takes something of a unique approach when it runs into legitimate sites that are unwittingly hosting links to malware, blocking just the link instead of blocking access to the entire legitimate site.

Paid competition

Valimaki noted that he is not aware of K9 users migrating up to Blue Coat's commercial enterprise offerings. Still, he did say that Blue Coat gets lots of requests from people with small office that wonder about how to buy K9.

Despite the potential allure of a small-business offering, Blue Coat does not have licensed version of K9 that it sells to small office users.

There are, however, a few different commercially available options for Web filtering that could benefit consumers and small offices.

Symantec offers Norton Safe Web, which provides site reputation and filtering capabilities. Security vendor Webroot also has filtering technologies for consumers and enterprises, which it extends to consumers through Webroot Parental Controls, and which enables users to set time limits on usage as well as blocking objectionable sites.

Both Symantec and Webroot declined to comment on their offerings' capabilities.

Challenges of Web filtering

Yet while Blue Coat says it's seeing K9 pay off, Valimaki said there's still a number of issues to sort out when it comes to Web filtering.

For instance, the industry has a difficult time getting its arms around what he called "gray" pages on the Internet -- the many marketing sites with links to wares like pharmaceutical products. Technically speaking, those pages are not malware, so Web filtering companies can't be sure how to categorize them. However, such link-heavy pages are often hit by users who are lured by search engine results. The sheer volume of those types of pages is a challenge, Valimaki said, as is the process of determining how they all should be treated.

"Five years ago, if you asked about URL filtering it was typically about blocking pornography from the workplace," Valimaki said. "While that remains a key component, blocking malware and suspicious stuff is now the talking point. "