Malicious software, also known as malware, is software designed to deliberately harm your computer. For example, viruses, worms, and Trojan horses are malicious software. To help protect your computer against malware, make sure you are using up-to-date antivirus and antispyware software.

Windows comes with Windows Defender, which can help protect your computer against malicious and unwanted software, such as spyware and adware. Windows Defender is installed and turned on by default.

However, Windows doesn't come with antivirus software. If you don't have up-to-date antivirus software on your computer, you should immediately install it because any computer that is connected to the Internet without antivirus software is vulnerable to attack. You can purchase antivirus software online by going to the Microsoft Antivirus Partners website.