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.