Windows Firewall can help prevent attackers or malicious software from gaining access to your computer through the Internet or a network. Now when you install Security Essentials, the installation wizard verifies that Windows Firewall is turned on. If you have intentionally turned off Windows Firewall, you can avoid turning it on by clearing a check box. You can change your Windows Firewall settings at any time via the System and Security settings in Control Panel.

Attackers are increasingly carrying out network-based attacks against exposed vulnerabilities before software vendors can develop and distribute security updates. Studies of vulnerabilities show that it can take a month or longer from the time of an initial attack report before a suitable security update is developed, tested, and released. This gap in protection leaves many computers vulnerable to attacks and exploitation for a substantial period of time. Network Inspection System works with real-time protection to better protect you against network-based attacks by greatly reducing the timespan between vulnerability disclosures and update deployment from weeks to a few hours.

Under the hood of Security Essentials is its award-winning protection engine that is updated regularly. The engine is backed by a team of antimalware researchers from the Microsoft Malware Protection Center, providing responses to the latest malware threats 24 hours a day.