Platform: Windows 7
Microsoft Security Essentials is a free product you can download to help defend computers running Windows 7 against viruses, spyware, and other malicious software.
Note: In Windows 8 & 10, Windows Defender replaces Microsoft Security Essentials, and is installed by default. Windows Defender runs in the background and notifies you when you need to take specific action. However, you can use it anytime to scan for malware if your computer isn’t working properly or you clicked a suspicious link online or in an email message.