Security software buying guide

These are mostly downloads from such names as Avira and AVG. But there's also the Microsoft Security Essentials anti-malware program that's available as a free download for XP, Vista, and Windows 7 computers.

These offer not only malware protection but add a firewall and in some cases, other extras such as a child filter. But none of the free suites we tested include some other features that are often found on pay suites such as anti-spam protection, built-in backup software, and a browser toolbar that will alert you when you're visiting sites that host malware.

Such suites, from brands that include Symantec and McAfee, promise comprehensive protection in one package. They offer not only malware protection but also a firewall, an anti-spam filter, and other extras. The latter usually include a child filter, often include a browser toolbar that will alert you when you're visiting sites that host malware, and sometimes include a file shredder and file backup software.

You typically buy the program online, either by downloading it or upgrading from a free trial version carried on your PC. You can use a suite on as many as three computers in the same household. Prices typically range from $40 to $80, and include a first year of service. After that, you'll typically pay another $40 to $80 per year to renew service.

These offer supplemental protection that you may want because your e-mail program isn't adequately filtering out unwanted messages. Often built into pay suites, free options include SPAMfighter at spamfighter.com, which we recommend.

Free security toolbars available for all major browsers provide extra protection against phishing sites, especially if you're using an older browser version or just want extra protection.

Deleting a file from your hard drive does not remove all electronic traces of it--which can allow someone who accesses or inherits your computer to recover some or all of the file's data. To eliminate that possibility, you need file-shredding software. Some pay suites include one, or you can download Eraser free from eraser.heidi.ie.

This feature blocks attempts to deliver malware via instant messages.

A firewall keeps malware from downloading and prevents a malicious Web site from grabbing data off your computer. The best firewalls protect you from incoming and outgoing threats, and pop up clearly worded alerts when a potential breach is detected, to help you decide if it's OK to let the data go through.

The filters provided by many e-mail programs or ISPs might be all you need to block unwelcome mail. The anti-spam feature on suites (and standalone, and often free, programs) offer supplementary assistance if too many junk e-mail messages are still getting through.

These block access to certain sites unsuitable for children.

If you're about to inadvertently divulge personal information, a privacy filter will provide a warning.

These toolbars can be placed into popular browsers to help prevent phishing.

This feature allows you to erase files to prevent their recovery from your hard drive.

A suite with this feature will periodically back up your files to another drive.

As long as you surf safely--that is, you never download software from unfamiliar sites (those downloads might carry malicious software) or click on e-mail links to access bank or other personal accounts (those links are favorite tools for cyberthieves)--the free anti-malware programs we recommend should adequately protect you.

The ones we tested did not include firewalls, but Windows 7's firewall was comparable to those in most suites. You can also add a firewall such as CheckPoint's free ZoneAlarm at http://www.zonealarm.com/security/en-us/free-upgrade-security-suite-zonealarm-firewall.htm.

Your vulnerability varies by your computer's operating system, though less than you might think. In our survey, Apple computers were much less likely than PCs to have been attacked by viruses and spyware, but Macs can transmit infected files to Windows PCs, including those connected to a Mac over a network in your home. Several manufacturers offer a Mac-compatible product, including Symantec, BitDefender, and Intego.

Some suites demand more resources than others. Machines with less than a gigabyte of memory might run too slowly with such gluttons. Similarly, some programs' scans take longer than others. If you have an older computer, it's even more important to look for products that score higher under "resources" in the Ratings (available to subscribers).

An advantage of a pay suite is that it simplifies your security regimen. It requires just one download and installation and a single upgrade to its database when necessary. Its single interface can also be easier to use than multiple stand-alone programs.

The extras you get with a suite include a built-in firewall, which can block attempts by malicious software to access data on your computer. In our tests, the firewalls in the best suites afforded slightly better protection than those built into Windows operating systems--though the latter offered adequate protection for most.

With free products, help is usually limited to online FAQs, forums, and tutorials. Most of the tested pay suites offer free e-mail and chat support. Most also offer phone support, though some charge for it. We can't comment on the quality of any program's tech support.

Easily downloaded for all major browsers, these provide extra protection against phishing sites. They should be used even with a Mac, especially if you're using an older browser version or just want extra protection. Try McAfee SiteAdvisor (www.siteadvisor.com) or, for XP, the Netcraft Toolbar (toolbar.netcraft.com).