Installing or switching antivirus safely

Before you start

A few minutes of preparation saves most of the trouble people run into.

• Install any waiting operating system updates and restart. Installing security software on a computer with pending updates is a common source of errors.
• Back up important files. Installation rarely causes data loss, but a fresh backup is good practice before changing system software.
• Find out what is already installed. On Windows, open Settings, then Apps, and look through the list for security products. On a Mac, look in the Applications folder.
• Find your account details for any existing product, so you can cancel its subscription if you are replacing it.
• Make sure you have the email address you will use for a new account, and access to that inbox to receive an activation message.

Download from the right place

Fake download sites are one of the most common ways unwanted software reaches home computers. They copy the look of a real vendor and offer an installer that bundles adware or worse. The safest habit is simple: type the vendor's address yourself, or use a link you trust, and check the address bar before downloading.

Signs that a download page is not the real thing include an address that is slightly misspelt or uses an unusual ending, a "download manager" that must be installed first, extra software pre-ticked during installation, and pop-ups telling you the download is urgent. Apple's Mac App Store and Microsoft Store are also legitimate sources for products listed there.

Links on Nexaline to Avast go to the vendor's site through an affiliate tracking address, which is disclosed beside each link. Wherever you start, check that the page you land on for the actual download belongs to the vendor.

Remove the old product first

Two antivirus products with real-time scanning running at once tend to slow the computer and can block each other. Windows handles its own built-in antivirus automatically, so you do not need to remove Microsoft Defender Antivirus. Third-party products are different and should be removed before a new one goes on.

On Windows

1. Open Settings and choose Apps, then Installed apps (on some versions it is called Apps and features).
2. Find the old security product, select the menu beside it and choose Uninstall.
3. Follow the product's own prompts. Some ask you to confirm in a separate window, or offer to keep settings; choose to remove everything if you are switching vendors.
4. Restart the computer when asked.
5. If the product does not uninstall cleanly, many vendors publish a dedicated removal tool on their support site. Download it only from the vendor's own site.

On a Mac

1. Check whether the product includes its own uninstaller, usually inside its folder in Applications or in its menu bar app.
2. If it does, use it, since dragging the app to the Bin may leave background components behind.
3. If it does not, follow the removal instructions on the vendor's support site.
4. Restart the Mac.

Install the new product

Installation steps differ between vendors, but the general shape is consistent.

1. Run the installer you downloaded. On Windows you will see a User Account Control prompt asking whether to allow changes; confirm only if the publisher shown matches the vendor.
2. Read each screen. Untick any additional software or browser extensions you did not ask for. Reputable installers make these optional.
3. Create or sign in to an account if the product requires one. Many vendors now link the software to an account. You may receive an email asking you to confirm, or activate, the account. Open it from your inbox rather than from a link elsewhere.
4. On a Mac, approve permissions. macOS asks you to allow system extensions or grant Full Disk Access in System Settings, under Privacy and Security. Security software generally needs these to scan properly. Grant them only to the product you just installed.
5. Let it update. Most products download the latest detection data straight after installation. Leave it connected to the internet until this finishes.
6. Restart if asked.

Check that it is working

Once installed, confirm that the computer sees the new product as its active protection.

On Windows: open Windows Security and choose Virus and threat protection. The page should name your new product and show that it is on. If it still names Microsoft Defender Antivirus as active, the new product may not have finished installing; restart and check again.

On a Mac: open the product and check its status screen, and confirm in System Settings, under Privacy and Security, that its permissions are switched on.

If you want to confirm that real-time scanning responds, the European Institute for Computer Antivirus Research publishes a harmless standard test file at eicar.org. It contains no malicious code; antivirus products recognise it by agreement so people can test their set-up. You do not need to do this, and if you do, read the instructions on the EICAR site first.

After installation

• Cancel the old subscription. Uninstalling software does not cancel its billing. Sign in to the old vendor's account and turn off automatic renewal or cancel, keeping a copy of the confirmation.
• Note the renewal date of the new subscription in your calendar, with the renewal price beside it.
• Review notifications. Most products let you reduce promotional messages without turning off security alerts.
• Keep Windows Update or macOS updates switched on. Third-party antivirus does not replace system updates.

Going back to built-in protection

If you decide a third-party product is not for you, uninstalling it is all that is needed on Windows. Microsoft Defender Antivirus normally switches itself back on once no other antivirus is registered. Open Windows Security afterwards and check that the Virus and threat protection tile shows a green tick. If it asks you to turn protection on, follow the prompt. On a Mac, the built-in protections keep running regardless of any third-party product, so removing the product is enough.

Common problems and what usually fixes them

If something goes wrong that you cannot resolve, the vendor's support pages are the right first stop. Be wary of support phone numbers found through search adverts or pop-ups; find contact details from the vendor's own site. The guide on fake virus warnings explains why.