Microsoft Security Essentials (MSE) (previously codenamed Morro) is a free antivirus software created by Microsoft that provides protection against viruses, spyware, rootkits, and trojans for Windows XP (x86), Windows Vista, and Windows 7 (both x86 and x64), free of charge. MSE replaces Windows Live OneCare, a commercial subscription-based antivirus service and the free Windows Defender, which only protected users from adware and spyware. It is geared for consumer use, unlike Microsoft’s upcoming enterprise-oriented product Microsoft Forefront.
Symantec and McAfee, two competing antivirus vendors, responded by claiming that MSE is not as good as their own software. AVG Technologies viewed MSE positively, stating it reinforced the company’s ideal of free antivirus software. Reviews were mostly positive, citing its organized interface, low resource usage, and its status as freeware.