What Is Malware?

What to do: Install updates, don’t download programs from websites, and stop and think whenever your computer asks for permission to make changes.

Malware is any harmful program, such as a virus. It can steal your passwords, lock up your files until you pay, or let someone else control your computer.

How to Protect Yourself

Do install updates when your computer asks. Most malware gets in through security holes that updates have already fixed. See Software Updates.

Do be careful online:

• Stick to websites you know and trust.
• Don’t click links or open attachments you weren’t expecting, even from people you know. Their account might have been hacked.
• Never download a program from a website and run it. Ask the sysadmin to install it, or install it with a package manager.

Do stop and think whenever a window pops up asking whether to let a program make changes to your computer. Malware usually needs you to click Yes on one of these. If you aren’t sure exactly what you’re approving, click No and ask the sysadmin. See Privilege Escalation for more.

Don’t buy or install antivirus software, paid or free (for example Norton or McAfee). It doesn’t protect well against modern threats, and it can add security risks of its own. The protection built into your computer (Microsoft Defender on Windows) is enough.