Now that Microsoft Security Essentials is generally available to consumers in 19 countries, we've had a chance to go over the data, and there are some very interesting results. Just in the first week we saw well over 1.5 million downloads of Microsoft Security Essentials, but the price (free to Windows users) is hard to beat!

Computers reporting detections up to October 6: almost four million detections on 535,752 distinct machines. The detections are eight times the machine count because many computers are infected with multiple threats.

Microsoft Security Essentials is available in 8 languages and 19 markets at RTM, which covers a lot of the PC using world. The geographic distribution of detections so far still closely follows the Microsoft Security Essentials Beta countries, and is ramping up in other countries that use the 8 languages.

Looking at counts of computers reporting detections by threat categories, we see that the order is different in each of the top three countries.  Trojans are the top detected category in the US, China has lots of potentially unwanted software threats, and worms (particularly Conficker) are very active in Brazil.  There are also many exploits being encountered in China, which may mean these PCs do not have the latest security updates.

The top threat families for these countries have remarkably similar curves, but very different family mixes.

China top families include several exploits (ShellCode, IFrameRef), the US has the trojans Wimad and rogue trojan FakeXPA at the top, while Brazil has worms Conficker and Taterf.

For family details, see the MMPC threat encyclopedia at http://microsoft.com/security/portal

Looking at the operating systems breakdown, we're seeing lots of Windows 7 using Microsoft Security Essentials, but a pretty even balance between OS'es:

The Windows 7 numbers are spectacular for an operating system that hasn't yet released for global availability.  Even better, about 1/3rd of Windows 7 Microsoft Security Essentials machines are 64-bit, which is even more resistant to malware than 32-bit due to PatchGuard.

By looking at detections divided by active Microsoft Security Essentials machines over the whole population, we see far more detections per XP machine, with the fewest from Win7.  This follows our usual observed trend of seeing less malware on newer OSes and service packs. 

In one short week, Microsoft Security Essentials's making a big difference to those people using it on their computers. If you don't have updated antimalware on your computer we strongly recommend giving Microsoft Security Essentials a try.

--Joe Faulhaber