The glory days of carefree Web surfing are over, due to the growing ranks of untrustworthy sites that bust your browser and drop ID-stealing malware onto your system. Fortunately, two innovative, free services--Scandoo (public beta) and SiteAdvisor--can help you surf the Web safely. Both use automatic crawlers to scour the Internet for potentially dangerous Web sites, and each uses color-coded icons to signify risk factors for the sites that appear in your Web search results.

I'm a big fan of SiteAdvisor's detailed analysis, seamless browser integration, and indicator icon for currently viewed sites. But Scandoo, through analysis and community feedback, can flag search results based on URL category filters (such as nudity).

Launched in March and snapped up by McAfee in April, SiteAdvisor is a free plug-in for Internet Explorer and Firefox that automatically color-codes both search results and sponsored links in Google, MSN, and Yahoo. A red icon indicates that the site clearly runs afoul of SiteAdvisor's tests for spam, downloaded malware, and links to other malicious sites. Yellow means the site is questionable; green means the site is clean. You can obtain more details and a link to all the testing data if you pass your mouse over the icon. A browser icon displays the color rating for the site you're currently viewing, as well. If a site is exceptionally bad, SiteAdvisor blocks access to it in Internet Explorer but not in Firefox.

To use the Scandoo service, you must run your searches through its Google-like Web site or install an IE 7 or Firefox plug-in that adds Scandoo as an option to either browser's integrated search box. You can get results from Google and MSN; support for Ask.com and Yahoo is coming.

Scandoo's analysis is far less detailed than SiteAdvisor's. You'll see a black bug icon to the left of results where Scandoo's crawler found a threat. You can mouse over the icon, but there's really no point--you'll get only a generic message saying the site 'may represent a potential web risk'. Also, Scandoo currently does not rate any sponsored links, though the company plans to add this functionality soon.

Scandoo's key advantage over SiteAdvisor is that it lets you flag sites using any of 26 different Web category filters. The service marks any search results that match your selected filters with a red icon. In our informal tests, we saw no significant flaws with Scandoo's site categorization. The service won't block the site in question, either, so you can still visit it if you want; you'll just receive some advance warning about its content.

SiteAdvisor says that it is looking closely at adding Web category filtering, but for now the feature is the deciding factor between the services. If you don't need such filtering, SiteAdvisor's deep analysis and seamless browser integration are far superior to Scandoo's generic warning message for search results only.