Microsoft Security Essentials has once again failed to make the grade for certification at AV-Test, an independent but non-required honor that most anti-virus programs enjoy. By extension, Windows 8's built-in virus protection, Windows Defender, likely suffers the same shortcomings as it is essentially a rebadged version of MSSE. The anti-virus utility marked its first failure for Sept/Oct.

Since its debut in 2009, Microsoft's no-cost anti-virus has remained free of advertisements, nagging reminders or required registration. This made MSSE an exciting alternative to long-time freebies Avira, Avast and AVG. MSSE quickly took off and gained a reputation as a top contender, once receiving excellent marks for its lightweight foot print, simple interface and detection/removal capabilities. In recent times though, MSSE has slipped – a lot.

AV-Test basically flunked MSSE for having the worst zero-day detection rates of any virus scanner. According to the organization, MSSE caught only 78 percent of freshly devised badware thrown at it in December – the industry average was 92 percent. In November, it did worse with only 71 percent. Microsoft's anti-virus also performed below-average for most other types of detection removal scenarios.

Bitdefender: Internet Security 2013, Trend Micro: Titanium Maximum Security 2013 and F-Secure: Internet Security 2013 rounded out the top three winners when it came to overall detection rates. When it comes to free anti-virus software, AVG edged out Avast for the tenth spot in overall protection. 

It wasn't all bad for MSSE though. Security Essentials did fare well in removing infections from critical system areas (12 percent higher than the industry average) and received a perfect score for avoiding false detections. The software also placed third for overall usability and performance.

AV-Test is an independent German organization who, amongst other things, rates anti-virus utilities based on various metrics every couple of months. AV-Test's certification is by no means an industry requirement, but their test results have served as a standardized way to benchmark anti-virus programs for a number of years.

Also on the list of non-certified AVs are PC Tools: Internet Security 2012 and Korean-made AhnLab: V3 Internet Security 8.0, which features its own custom AV engine.