Microsoft Security Essentials

Microsoft Security Essentials (MSE) is a discontinued antivirus software (AV) product that provides protection against different types of malicious software, such as computer viruses, spyware, rootkits, and Trojan horses. Prior to version 4.5, MSE ran on Windows XP, Windows Vista, and Windows 7, but not on Windows 8 and later versions, which have built-in AV components known as Windows Defender. MSE 4.5 and later versions do not run on Windows XP. The license agreement allows home users and small businesses to install and use the product free of charge.

Built upon the same scanning engine and virus definitions as other Microsoft antivirus products, it provides real-time protection, constantly monitoring activities on the computer, scanning new files as they are created or downloaded, and disabling detected threats. It lacks the OneCare personal firewall and the Forefront Endpoint Protection centralized management features.