Version 4.0 of Microsoft's Security Essentials (MSE) anti-malware and anti-virus software for Windows has been released. Previously only available as a beta, the new version of the program looks very similar to the previous 2.x branch; most of the cosmetic changes are to be found only under the Settings tab.

Improvements in V 4 include reduced system requirements and faster virus removal, better cleanup and removal. It still sorts threats into four levels. Severe or high threats will be automatically sent to quarantine without warning. Threats considered medium or low level will be left to the user to choose (setting > default actions).

Real time scanning has been cut back from 5 options to just one: previously, scan modules such as the one for checking downloads could be disabled individually. Now, the only choice is to completely disable real-time protection. Another change is that files in the quarantine folder will automatically be deleted after 3 months. This option existed in previous versions, but was disabled by default.

Feedback is now through "Microsoft Active Protection Service" (MAPS). The default continues to be the "Basic membership" plan that will send basic information on any detected malware to Microsoft. As in MSE 2.0, users can completely opt out of MAPS or choose to become "Advanced members", which enables MSE to pass on to Microsoft considerably more detailed information about any unknown programs that are found.

MSE 4 is compatible with Windows7, Vista (SP1 or SP2), or Windows XP Service pack 3. It is available to download free of charge, which allows installation for business systems up to 10 users. During installation, the application will check if the user's Windows license is genuine. On PCs that don't have the virus scanner installed, Windows Update will offer to install Microsoft Security Essentials 4 as an optional update.