Microsoft has today both announced and released a beta version of its free Security Essentials anti-malware software. The new version of the lightweight anti-virus, anti-spyware software includes more protection against network-based attacks.

The network protection has two parts. Microsft Security Essentials now integrates with Internet Explorer to better protect against Web-based threats. This allows the program to prevent malicious scripts from running. The current version can detect such scripts when they get written to Internet Explorer's cache, but that may be too late to protect the user.

For users of Windows Vista and Windows 7, the new Security Essentials provides protection against network exploits, by inspecting network traffic and blocking any suspicious connectivity. This feature isn't available for Windows XP, as it depends on the Windows Filtering Platform facility that was introduced with Windows Vista. Windows Filtering Platform allows programs to plug themselves into the networking subsystem and monitor any network traffic in a robust, high performance way. This provides protection above and beyond that offered by the Windows Firewall (which the new version of Security Essentials offers to enable during installation), as it can guard against attacks made on software that's allowed through the firewall.

The beta is available on a first-come, first-served basis on Microsoft Connect; the beta program only has a limited number of places. Microsoft claims that the beta is only available to customers in the US, Israel, Brazil, and China; nonetheless, it successfully downloaded and installed for me (I'm based in the UK). Future updates will be delivered through Microsoft Update.

Microsoft Security Essentials has already become popular thanks to its low resource usage and discreet interface. This network-based monitoring represents a significant broadening of the Security Essentials' scope. By guarding against network attacks in addition to malware, the program is becoming something of a must-have for Windows users.