Is it safe or isn't it? Whether you're asking this question about your own system, a site you'd like to visit, or a link you're tempted to click, you need the right tools to help you understand the level of risk involved. These utilities appraise the situation and deliver an informed assessment of where you stand.

AOL Active Security Monitor
Not being a big fan of AOL in general, I was initially leary about downloading and using this free tool. But this simple, straightforward application looks at the security of your PC, reports on what it finds, and makes recommendations. It checks to see if you have antivirus software installed and, if so, whether the definitions are up to date. Then it does the same for antispyware, tests whether you have a firewall enabled, and checks for peer-to-peer software that could pose a danger. The monitor doesn't have any protective capabilities itself, but it warns you if you need some. Be aware, however, that the software doesn't work with Windows Vista. And take its recommendations with a grain of salt: It touts for-pay AOL software such as the AOL Privacy Wall over free software that may be better. Still, if you're looking for some quick security recommendations, it's worth the download.

McAfee SiteAdvisor
On the Web, unlike in the real world, it can be hard to recognize a bad neighborhood when you're wandering around in it. There are no boarded-up windows, no empty storefronts, no hard-looking men lounging on corners or in doorways. In fact, the prettiest and most inviting Web site may harbor all kinds of malware. That's where the McAfee SiteAdvisor comes in. It warns you when a Web site that you're about to visit -- or are already visiting -- may be dangerous. You install it as an Internet Explorer toolbar or as a Firefox plug-in. Then when you search with Google or some other search engine, it displays color-coded icons next to each search result, indicating whether the site in question is safe (green), questionable (yellow), or clearly unsafe (red). It checks sites for downloads that may be dangerous, and for evidence that they will send you spam if you give them your e-mail address. The toolbar offers similar reports about the sites you're currently visiting.

LinkScanner Lite
This is another good tool for determining whether a Web site harbors dangerous content. Open LinkScanner Lite and type in a site URL, and the utility checks the site for dangerous scripts, bad downloads, and other hazardous content. It also warns you about phishing sites and other potentially fraudulent online operations, and it integrates with search sites in much the same way that McAfee Site Advisor does, putting icons next to search results to indicate whether they are dangerous or not. Unlike Site Advisor, though, it doesn't check whether sites harbor adware or spyware.

Internet Threat Meter
Every day, it seems, new threats hit the Internet. Symantec's Internet Threat Meter keeps you informed about the latest arrivals and includes a link to a Symantec site where you can get more information and find fixes. The program runs as a nifty little widget in Windows XP, or as a Sidebar Gadget in Windows Vista, gathering data about the latest threats and reporting the results to you.

Trend Micro HijackThis
Like it or not, no single antispyware program can detect and eradicate all spyware. Consequently your favorite antimalware utility doesn't fully protect you. If you suspect that you've been victimized by spyware, but you haven't been able to track down the source of the trouble using your usual diagnostic software, give HijackThis a try. It thoroughly analyzes your Registry and file settings, and creates a log file reporting its results. If your system is infected with spyware, that file will contain clues about the particular type you're dealing with. Though an expert can analyze the log to try to track down the problem, you shouldn't try to do any advanced analysis yourself unless you possess relevant expertise. Instead, simply upload the log file to a HijackThis Web site, and ask the community there to analyze it for you.