An endpoint security study released this week by independent German lab AV-Test evaluated 28 antivirus products against three criteria: protection, repair and usability. Products could earn up to six points in each category for a possible total of 18 points. Bitdefender, Kaspersky Lab and Symantec lead the field while the protection packages from Avast, F-Secure and GData share fourth place.

All of the software earned top scores of 15.2 points or more nearly five points higher than the overall result obtained by Microsoft's Windows Defender or Security Essentials when used together with the Windows Firewall, reported AV-Test.

"This proves that the use of external security solutions can lead to a massive improvement when it comes to system protection."

The best at stopping malware, as measured by the lab's "protection" tests came from Bitdefender, F-Secure and Kaspersky. The best free programs were Avast and AVG but only made it to eighth and twelfth place respectively," said AV-Test.

"The Windows Defender provided by Microsoft in its operating system set a very low benchmark value with a detection rate of just 79 per cent.

Microsoft's free endpoint security software, however, did earn top marks in usability, which only five other tested products managed to equal.