German antivirus lab AV-Test has failed to give Microsoft's free security software any certification.
The group, which tests security suites against real world threats and reports the results every two months, looks at the software's ability to protect, repair, systems and general usability.
To receive certification, the product needs a total of 11 out of the 18 possible points.
Of the 23 products tested, 16 scored worse this time and Microsoft Security Essentials failed completely.
AVG Anti-Virus Free Edition, VIPRE Internet Security, and Microsoft Security Essentials all scored three full points lower than their previous test. Microsoft scored 10.7 and failed and the other two just managed to scrape a pass.
Microsoft scored just 1.5 points for protection which makes it about as good at defence as the English football team. It was nearly useless at zero-day threats, with a protection rate below 70 percent where top products managed 100 percent.
The best out of the box was Bitdefender Internet Security with 17 of 18 possible points.
F-Secure Internet Security and Kaspersky Internet Security both had 16.5 points last time and in the current test they dropped to 15.5 and 15.0 respectively. Norton Internet Security also stands at 15.0, down from 15.5.
The results were quite similar. F-Secure Client Security topped this group, with 16.5 points, while Microsoft's Forefront Endpoint Protection bombed, earning just 9.5 points.
The message appears to be that if you are relying on Microsoft Security Essentials you could have your machine packed full of viruses.
You can see the test here.