Microsoft Security Essentials

Microsoft Security Essentials (MSE) is an antivirus software (AV) product that provides protection against different types of malicious software such as computer viruses, spyware, rootkits and Trojan horses. Before version 4.5, MSE ran on Windows XP, Windows Vista and Windows 7, but not on Windows 8 and later, which have built-in AV components. MSE 4.5 and later do not run on Windows XP. The license agreement allows home users and small businesses to install and use the product free of charge. It replaces Windows Live OneCare, a discontinued commercial subscription-based AV service, and the free Windows Defender, which until Windows 8 protected users from only adware and spyware.