Microsoft's anti-virus, Microsoft Security Essentials, could be manually installed on computers running Windows 7 and earlier. Windows Defender was an anti-spyware application that could be installed as well. Since Windows 8 both of those have been combined into "Defender" and pre-installed as a component of Windows 8/8.1 and 10 operating systems. Thus, if you have Windows 8/8.1 or Windows 10 running on your computer, you already have anti-virus/anti-spyware protection running by default.
A few questions from our community:
1. I thought that it is not good to run two anti-virus applications. I have Windows 8 (or 10) on my new computer, but McAfee was also preinstalled. Can I keep McAfee? Can I install an anti-virus application from another vendor?
Yes, you can install another anti-virus. Defender should automatically disable itself when another AV comes onboard and is activated. You can always check via Windows Control Panel or by searching for Defender. Go to Defender's Settings Tab. Click Real-time protection on the left. Make sure "Turn on real-time protection" is unchecked. Open your new AV and confirm that its protection is running.
*NOTE: If you are installing an anti-virus (ESET, Avast!, Kaspersky, etc.) other than the one pre-installed by Lenovo, make sure you have removed all components of McAfee, Norton, etc.. before installing a new one. It is advisable to use the vendor's instructions and removal tool for doing that. If there is a question please post on Lenovo's Security & Malware forum. The helpers there can provide instructions and/or a link to the vendor's detailed instructions.
2. How does Defender update?
Defender will update daily if you have selected for Windows to provide automatic updates. If you do not enable automatic updating in Windows, you can manually update Defender. Simply open Defender and click the Update button on the Updates Tab. The Windows 10 Anniversary Update added a new feature in the event that signatures are delayed for some reason: Cloud protection still is updated and running.
3. How do I exclude specific files from Defender Scans?
Again, by searching for Defender you can access its settings. You may want to create a shortcut on your Taskbar if you change settings often or manually update each day. Files to exclude, as well as which drives to scan, can be found on the left of the Settings tab.
4. I see various options at Settings, but how do I schedule scans, other than Defender's default? I don't want Defender to scan regularly. I would rather run scans on demand. How can I change this?
Defender's default Quick Scans are short so they do not inconvenience the user. Currently, there isn't a setting in Defender to use on-demand scanning in Windows 7/8/8.1. However, there is a way to turn automatic scanning off.
* Open Task Schedule (Search Schedule Tasks. It will be under Settings.)
* Double-click to open the Task Scheduler Library on the left side pane, it is located under Microsoft -> Windows Defender. Look for MP Scheduled Scan. Click on that. At the bottom of the right side bar it can be disabled.
[For Windows 10 users, on-demand scanning became possible with the Windows 10 Anniversary Update in August 2016.]
5. What Is Windows Defender Offline Scan?
This new component that arrived in the Windows 10 Anniversary Update is actually an anti-virus boot feature included for Windows 10.
To run this in Windows 10:
1. Go to Settings > Update & Security > Windows Defender.
2. Scroll down to “Scan Offline”. Click the button under Windows Defender Offline.
3. The scan for malware will begin. It may take 15-20 minutes, so be patient. When the scan is finished if any malware is found, you will see a prompt to clean it using Windows Defender Offline. If no malware is found, your computer will automatically boot back into Windows 10.
For Windows 7/8/8.1 Defender Offline can be downloaded. It is recommended to use a different (clean) computer for the download so that it can be transferred to the infected one. Running the downloaded msstool64.exe (for 64-bit Windows) or msstool32.exe (for 32-bit) file will create installation media on a USB drive, or burn it to a CD or DVD. It is also possible to create an ISO file, which you can burn to a disc yourself using your preferred disc-burning program.
2. Scroll down to download either the 32-bit or 64-bit version depending on whether your PC is running a 32-bit or 64-bit version of Windows. ( How to tell) The tool will create Windows Defender Offline media containing the latest virus definitions. * Note: If you have any important files on the USB drive back them up. The drive will be reformatted and all data on it will be erased!
3. Following the download, remove the USB drive or CD. Insert it into the infected computer, and boot the computer. If it does not boot from the media after you restart it, you may have to press a key to enter a “boot devices” menu or change boot order in the computer’s UEFI firmware or BIOS. See: https://support.lenovo.com/us/en/solutions/ht117661.
4. After the scan and cleaning are complete, remove the Windows Defender Offline media, and reboot your computer.
[Update 8/14/2016: With the Windows 10 Anniversary Update, Defender has been revamped. Along with other enhancements, there is a new Defender icon, on-demand scanning, release of Windows Defender Offline (for running offline scans see #5 above), Block at First Sight, enhanced notifications, and potentially unwanted application (PUA) detection. One great new feature is that if signatures are delayed, cloud protection still is updated and running. If you have questions or comments about Windows 10's 2016 changes to Defender's core UI, feel free to post HERE in the Security & Malware Discussion Forum.]