01/25/2013 04:04 pm ET Updated Mar 27, 2013

The World's Most-Used Security Software Fails Another Security Test

For the most popular anti-virus software in the world, Microsoft Security Essentials isn't very good at protecting computers against malware. For the second time in a row, the security software has failed independent testing by AV-Test, missing out on the testing company's coveted certification.

According to Opswat's Market Share Report for anti-virus software, Microsoft has by far the highest market share in North America, with 37 percent of the market, and 20 percent of the market worldwide, making it the most popular anti-virus software worldwide. This isn't a huge surprise, since most computers with a Windows OS come with Security Essentials installed, not to mention that it's free for Windows users. However, if AV-Test's scores are accurate, it means that a large portion of the world's computer users are not being properly protected.

How Microsoft scored in protection

AV-Test, a well-known independent testing lab in Germany, conducts a new round of "real-world" testing on various security software suites every two months. In the two most recent tests, which span from September to December 2012, Microsoft scored too low to be certified by AV-Test. To put it in perspective, 22 other anti-virus suites were certified in this round of testing, and only three failed.

So how did Microsoft Security Essentials score? To start, they had the lowest score for protection out of all the security suites tested, scoring only 1.5 out of 6. They scored only 71 percent on protection against zero day malware threats, which includes malicious software that has yet to be analyzed and rolled into an antivirus program's definition files. They also scored only 92 percent in detection of malware that had been discovered in the past 2-3 months.

So how do these scores compare? The top-rated security suite, Bitdefender (which does not even rate on Opswat's Market Share Report), scored a perfect 100 percent for each of these categories.

In addition, Microsoft also had one of the lowest scores in repair testing (3 out of 6), which tests how well software cleans and repairs a malware-infected computer.

On the plus side, Microsoft had one of the highest scores for usability, according to AV-Test. They scored a 5.5 out of 6 in independent testing, with high marks for both performance (not slowing down your computer) and avoidance of false detections.

What the scores mean

It depends on whom you ask. Microsoft claims that AV-Test used malware sample tests that 99.997 percent of their users had never seen, and that their own internal testing better informs them on what malware to protect against. And, up until September 2012, Microsoft had consistently earned certification from AV-Test, although none of their previous scores were incredibly impressive.

On the other hand, 22 other security software suites were better able to block the malware sample tests that AV-Test used. And AV-Test is well-known and respected for their anti-virus testing.

Basically, it means that Microsoft Security Essentials probably does a pretty good job of protecting you against most malware attacks, especially for a free software offering, but you might want to consider switching to one of the other 22 security software suites that did pass the test, just to be on the safe side.