Most viruses are easy to get rid of. Just open your antivirus scanner, wait for it to collect results, and then delete whatever it finds. Sometimes, however, the virus just won’t go away and no conventional antivirus solution helps.
So what to do with annoying, hard-to-remove viruses? Antivirus software includes a whole category of tools that scan before starting the operating system. Often called bootable antivirus programs, they scan files and remove viruses before they even have time to open.
Below are the best ways to remove viruses before starting the operating system. If you are not familiar with this process, we will go through all the steps, including how to load the scanner and what to do next so that it starts at startup instead of your operating system.
Council. If you are frequently infected with viruses, learn how to protect your computer from hackers and malware.
How does this bootable antivirus work
There are two types of bootable antivirus software. One is a standalone program that needs to be installed on a USB device or drive and then loaded from it when the computer starts up. What happens is that the software on that device or disk runs instead of your operating system, and then you can run a scan and remove viruses from there.
The other type installs on your computer and works like a regular antivirus solution, but it also has the option to run a scan at boot. Just restart your computer and let the scan take its course. This is an easier method for most people, but it will not work if the virus is so dangerous that it prevents the operating system from starting correctly.
Depending on your specific situation, you might want to use one method instead of the other, so we’ll look at how to use both.
Use a disk or a USB device
The first type of bootable antivirus software is an ISO file that you download to your computer and then put on a separate device so that you can boot from it.
There are many options for this type, including Trend Micro Rescue Disk, Comodo Rescue Disk, Anvi Rescue Disk, Kaspersky Rescue Disk, and Windows Defender Offline Some of these programs require a disk, while others can be used with a USB flash drive.
We will use Adaware Rescue USB as an example because it works with Windows 7 and newer Windows operating systems, can update its definitions before scanning, and supports custom scanning.
- Follow the link above. to download the ISO file. Choose the amd64 version if you have a 64-bit computer, otherwise use x86 for a 32-bit version. This software is over 1 GB and may take some time to download. Some of the other AV boot programs listed above are much smaller if time is an issue.
- Also download Rufus, the program we’ll be using to host the software on the flash drive. There is a portable version on the download page if you don’t want to install it.
Note. This software can also be loaded from disc, so if you prefer to do so, you can burn the program to a CD using ImgBurn and then proceed to the BIOS step below.
- Connect your USB device to your computer. Make sure you are ok with wiping the entire disc. Otherwise, copy the content to another location temporarily.
- Open Rufus and select this device from the first drop-down menu.
- Select SELECT and then open the ISO file you just downloaded.
- Change other parameters as needed.
- Click START.
- Select OK on the format alert to begin copying the bootable antivirus tool to disk.
- Close Rufus when the process ends.
- Restart your computer and enter BIOS. Follow this link to learn how to change the boot order so that you can boot from a USB device instead of the OS.
- Click OK at the Adaware Live CD prompt.
- Select UPDATE DEFINITIONS to ensure that you have the latest techniques required to detect threats.
- Select the scan type. Adaware Live CD supports boot sector scan, quick scan, full scan, and custom scan. If you know which folders you want to scan for viruses, use the custom scan option. Otherwise, it is recommended to run a full scan to make sure malware is detected no matter where it is hiding.
Use a regular antivirus with a bootable option
If the above procedure takes too long or is too complicated, or if you don’t have a floppy drive or free flash drive, you still have another option.
Some common antivirus programs that are installed have the ability to run scans and remove viruses when you restart your computer. They work in much the same way as the above mentioned bootable AV tools, but they are much easier to use and they do all the scanning and removal automatically.
Some free antivirus programs with on-download scanning capabilities include Avast Free Antivirus, Adaware Antivirus, and AVG AntiVirus Free All of these programs work slightly differently; Avast and AVG require you to specifically enable this feature, while Adaware will automatically scan for viruses on boot.
Let’s take a look at how to use the free Avast scanner to remove viruses before operating system launch:
- Download the program from the link above and then install it. Watch out for any additional suggestions you may see during installation, such as installing third-party programs. All you really need to perform virus cleaning functions is Avast.
- Select “Security” in the left pane.
- Select Virus Scan.
- Select OPEN NOW under Startup Scan.
- Click the settings / gear icon in the upper right corner to open Avast’s startup scan settings.
- Change any settings to your liking. As you can see in this screenshot, you can adjust the sensitivity of the scanner, scan for potentially unwanted programs, open archives to scan inside them, scan all hard drives connected to your computer, or just the system drive, and check for viruses in programs. which usually automatically start with the operating system.
You can also choose what happens when a threat is detected: Avast can try to fix it without deleting the file, or you can move the file to the quarantine area or simply delete it.
- Click the exit button in the upper left corner of the settings to return to the boot scan screen.
- Select RUN ON NEXT PC REBOOT. This screen also includes an Install Custom Definitions link that you can click to download additional definitions that should help you find viruses during the download process.
- The next time you restart your computer, Avast will scan for viruses before launching the operating system and will fight threats in any way specified in the settings. Note that only on next reboot will it scan for viruses; to have it run the boot scan again on the next reboot, just repeat these steps.
This is what it looks like when scanning for viruses while downloading Avast. This can take several hours, depending on how many files you need to check.
Pay particular attention to the TXT file listed on the line in the report file. This should be the same for all computers; this is where you can go after the OS starts to see what Avast Free Antivirus has detected and removed.
You can stop this scan at any time by pressing the Esc key. It will briefly tell you how many files have been scanned and if any infections have been found, and then your computer will normally reboot into the operating system.