New computers almost always come loaded with the trial version of a software suite designed to thwart spam, viruses and spyware. But Consumer Reports’ latest tests of 11 security suites show that not all of them deliver enough protection to justify paying $50 or more for the continued protection after the trial period.

CR also found spotty performance for some anti-phishing toolbars built into suites and integrated into browsers.

CR tracked how rapidly the programs addressed actual threats newly discovered by security researchers. In addition, CR looked at programs with modified badware (spyware and adware) and also evaluated whether programs wrongly identified benign files as threats, which might prompt users to delete an important e-mail or a system file that the machine needs to operate.

For optimal protection, CR recommends that users consider BitDefender, $50. CR’s tests revealed it was consistently very good in performance and fairly rich in features, including the best array of antivirus tools of the high-rated suites. McAfee’s Internet Security Suite with SiteAdvisor, $50, is a fine choice for a newer computer. It performed comparably to BitDefender and is among the most effective against spam and phishing.

Users who practice careful computing and want to protect their computers without paying fees should consider free software. CR’s testers combined three free online security programs – Avira AntiVir Personal Edition Classic 7, Microsoft Windows Defender and SPAMfighter Standard – and assembled them into a makeshift suite that actually performed better than some low-rated suites. The freeware suite lacks the optimal protection and rich features of the best suites, but it provides decent protection.

How to choose

¢ Assess protection needs. Basic protection offered by free software may suffice if everyone with access to the computer follows security-minded practices, including never downloading software from unfamiliar Web sites and never opening links in e-mail to access personal accounts.

¢ Consider performance. The best programs CR tested this year detected 80 percent or more of CR’s modified threats and updated their databases within a day or two to detect all the actual threats. The worst program allowed 60 percent or more of the modified viruses to slip by and had not detected most of the actual threats by the end of the test period.

¢ Favor suites over stand-alones. One reason suites do so well, CR’s tests suggest, is that they provide slightly better overall protection against viruses, spyware and adware than using several programs that each fight a single threat.

¢ Consider processing power. Some suites demand more of the computer’s power than others. Machines with less than a gigabyte of memory may run too slowly with such gluttons.

¢ Check for incompatibilities. CR found some suites easier to install and configure than others. Before buying, check software forums, including the security and privacy forum at www.ConsumerReports.org and those on software vendor Web sites to see whether others are having problems.

¢ Protect even a Mac. While Macs are far less vulnerable to viruses and spyware, they can transmit infected files to Windows users. Mac owners should use at least one anti-phishing tool.