Microsoft has released a new version of Security Essentials offering free protection for non-pirated Windows XP, Vista and 7 PCs.
The update will be made automatically available to existing users.
One reason Microsoft may be hush-hush on the update was that its initial launch in 2010 drew criticisms from Trend Micro that bundling it as an option in Microsoft Update was anticompetitive.
Spanish security firm Panda criticised it for diluting diversity and only making it available to genuine Windows customers.
Regardless, Security Essentials has quickly become one of the most popular free antivirus products, growing its worldwide share from 7 per a year ago to 10 per cent today, making it the third most popular antivirus product in the behind Avast, Avira and AVG, and slightly ahead of ESET and Symantec, according to a recent market share analysis by OPSWAT.
In the US it is second only to Symantec, recently bumping off AVG for second place with 14.92 per cent market share.
The free antivirus software can be downloaded here and is available for small business with up to 10 PCs. Any organisation larger than that is directed to its Forefront Endpoint Protection suite. The free product is part of its genuine Windows program.
A Microsoft spokesperson told Microsoft blogger Mary Jo Foley the service update MSE 4.0 improved performance, improved automated threat quarantining and contained minor bug fixes.
Despite its successful take-up, a test prior to the latest MSE update by Austrian AV testing company AV-Comparatives ranked MSE last amongst 20 well known security products (PDF). MSE’s detection rate was 93.1 per cent against “almost 300,000 recent” malware samples. This compared with G Data, AVIRA, Kaspersky, Sophos, F-Secure, Panda, Bitdefender, BullGuard and McAfee which all scored above 98 per cent.