For a long time Microsoft kept well away from anti-malware software, perhaps worrying about more competition troubles, as it had with bundling Internet Explorer. Microsoft Security Essentials 4 (MSE 4) isn't yet bundled with any version of Windows, but it is free for home and small business uses, like AVG Anti-Virus Free Edition 2012 orAvast! 7 Free Antivirus.

Microsoft Security Essentials 4 works with Windows Defender, which defends against spyware, but instead concentrates on viruses, rootkits and Trojans. Once the program's installed, the interface is very simple, just a single pane with four tabs, labelled Home, Update, History and Settings.

The Home tab enables a manual scan – quick, full or custom – and to set an automatic schedule. Update shows version and date info on virus definitions and enables a manual update. History is a bit of a misnomer in Microsoft Security Essentials 4, as there's no built-in log of scans or results – though any positive hits and actions from a scan are recorded. If you just need to know a scan has completed, you have to delve into Windows Event log, which isn't something most people will do lightly.

The settings tab of Microsoft Security Essentials 4 offers most of the usual controls, though the default scheduled scan is at 2am on a Sunday, so assumes you leave your PC on over the weekend. Many people will want to scan more than once a week, too.

When we performed a scan on our 50GB test file bundle using Microsoft Security Essentials 4, we had quite a surprise. The program claimed to have scanned 1,251,750 files, over five times as many as any other AV program we've tested and a whole lot more than the 8,780 Windows itself claims are in the test folders. Even including files in Zip archives within the bundle, which Windows doesn't count but MSE does, it's hard to see where this figure comes from.

Perhaps because the ‘file count' is so high, Microsoft Security Essentials 4 took 2 hours 42 minutes to scan them, well over twice as long as any other product we've reviewed. A repeat scan took slightly longer at 2hr 45min, but the scanner doesn't put a big burden on a system, with only a 38% increase in copy time.

AV-Test has evaluated Microsoft Security Essentials 4 and scored it 13.5/18. This compares with 14.5 for Avast Free Antivirus 7.0 and 15.5 for AVG Free 2012.

Perhaps more worrying is that Microsoft Security Essentials 4 drops off to 2.5/6.0 in the Protection category.

Although it scored 100% at detection of widespread malware and slightly better than average spotting 2-3 month old threats, it was a long way behind in zero-day detection, scoring 76% and 80% in consecutive months, against an average of 88%.

All this means that top protection from brand new malware will be better provided by one of the other free AV applications.

Although it's free, make sure you download Microsoft Security Essentials 4 from a reliable source. The application is said to be the second most popular AV software in the world, which has attracted imitations designed for less altruistic purposes.


It's hard to be critical of a product which is completely free, except when there are alternatives at the same price, which perform as well or better. Microsoft Security Essentials 4 is a good application and very easy to use, but its speed and, more especially, its protection against zero-day attacks, mean it's not the best.