Using a flash drive or USB stick is very convenient for transferring files between computers or storing data you want to take with you. However, flash drives can also spread computer viruses if they become infected. Taking some simple precautions can help protect your flash drive and the computers you use it with from viruses.
Why are flash drives vulnerable to viruses?
Flash drives are prone to spreading viruses because they are rewritable storage devices that are frequently connected to different computers. This makes it easy for viruses to spread from an infected computer to the flash drive, then to another computer when you plug it in. Viruses can also spread through infected files copied onto the flash drive.
Some factors that make flash drives vulnerable include:
- Portability – Flash drives are designed to be portable and used with many different computers. This mobility also makes it easy for viruses to spread.
- Autorun feature – Flash drives may have the autorun feature enabled, which automatically runs programs or opens files as soon as the drive is connected to a computer. This can trigger viruses.
- Lack of security – Flash drives typically do not have built-in security. There is no antivirus software scanning for threats.
- Removable media – As removable storage devices, flash drives can pick up viruses from infected computers, then pass them on to clean computers.
How do viruses get on flash drives?
There are a few common ways that viruses can infect and spread through flash drives:
- Infected computer: If you connect your flash drive to a computer that has viruses or other malware, those infections can easily spread to the flash drive.
- Infected files: If you transfer infected files from a computer onto the flash drive, those files can pass the infection on when opened on another computer.
- Autorun viruses: These viruses are triggered as soon as you plug in an infected flash drive. They automatically run malicious code to infect the host computer.
- Internet file downloads: If you use your flash drive to download files from the internet, there is a risk of unknowingly downloading virus-infected files.
How to check if a flash drive has viruses
If you suspect your flash drive may be infected, there are some signs to watch out for:
- Problems accessing files on the flash drive
- Unexpected pop-up ads, messages or lagging/crashing when the drive is plugged in
- Antivirus software detecting an infection on the flash drive
- Strange files you don’t recognize suddenly appearing on the drive
- Increase in the number of files, but no increase in the used storage space
- Changes to file sizes, timestamps or icons
To thoroughly scan for viruses, use antivirus software. Connect the flash drive to a computer with updated antivirus software installed. Run a full scan of the flash drive. This will detect and remove any viruses found.
Steps to make a flash drive virus-free
Here are some key steps to secure your flash drive and prevent virus infections:
- Use antivirus software – Install antivirus software on every computer you use the flash drive with. Schedule regular virus scans of the flash drive. This will detect and remove any infections before they can spread.
- Disable autorun – Turn off the autorun or autoplay feature on the flash drive. This prevents programs running automatically when you plug it in, which blocks some viruses.
- Safely eject drive – Always properly eject the flash drive before unplugging it from a computer. This prevents file corruption that can happen if you just pull out the drive.
- Avoid suspicious files – Don’t copy any suspicious unknown files onto your flash drive. Scan files with antivirus software before copying them.
- Password protect drive – Add password protection to your flash drive. This prevents unauthorized access that could lead to infection.
- Back up data – Regularly back up important data stored on the flash drive. This gives you a clean copy if your drive does get infected.
Use antivirus software
The best protection against flash drive viruses is using antivirus software. Install antivirus on all computers you connect the drive to. Top antivirus programs like Avast, AVG and Bitdefender all provide excellent virus scanning and removal.
Update the antivirus software regularly and set up automatic scans. Quick scans can be run each time you plug in the flash drive. Schedule full antivirus scans at least weekly too.
Many antivirus tools also have USB scanning modes specifically designed to detect threats on flash drives and other removable media. Turn this feature on for maximum security.
Disable the autorun feature
The autorun or autoplay feature allows content on a flash drive to run automatically when you plug it in. This is convenient but also poses a major virus risk.
Disabling autorun prevents malicious programs from automatically infecting the computer. It’s an important safeguard against viruses spreading via flash drive.
To disable autorun on Windows:
- Open the Start menu and select Run
- Type “gpedit.msc” and hit Enter to open the Group Policy Editor
- Navigate to: Computer Configuration > Administrative Templates > Windows Components > Autoplay Policies
- Double click on “Turn off Autoplay”
- Choose “Enabled” and hit OK to turn it off
On Mac OS:
- Go to Finder > Applications > Utilities > Terminal
- Type “defaults write com.apple.autoplay DisableAutoplay -bool true”
- Press Return and quit Terminal
Safely eject the flash drive
Never just pull out your flash drive without properly ejecting it first. This could corrupt files or leave data unfinished writing to the drive.
Damaged files are more vulnerable to viruses. Always safely eject the flash drive before unplugging it. In Windows, right-click on the drive icon and select Eject. On Mac, drag the drive icon to the Trash.
Waiting for the safe removal notification before disconnecting protects file integrity and reduces the risk of file corruption issues that can enable viruses.
Avoid suspicious files
To prevent your flash drive inadvertently becoming infected, use caution when transferring files onto it:
- Don’t copy any unknown files of uncertain origin onto the drive
- Scan files downloaded from the internet with antivirus software before copying them
- Only transfer files from trusted sources
- Watch out for fake software downloads that may contain viruses
Keeping malware off your flash drive in the first place is the most effective way to stop viruses spreading.
Password protect the drive
Adding password protection helps keep your data secure if your flash drive is lost or stolen. It also blocks viruses or other threats from infecting the drive.
Encrypted flash drives require a password before they can be accessed or files can be transferred on/off the drive. This acts as an access control to stop unauthorized software running.
On Windows, BitLocker is built-in encryption software that can password protect flash drives. There are also various third party encryption tools available.
Back up your data
As an extra precaution, you should also periodically back up important data stored on your flash drive. Maintaining a separate backup allows you to securely wipe and reformat the drive if it does get infected, without losing your data.
Cloud backup services like Google Drive or Dropbox provide an easy way to back up your flash drive files offsite. External hard drives also work for local backup copies.
How to remove a virus from a flash drive
If your flash drive does become infected, quick action can help prevent the virus spreading further:
- Isolate the infected drive – Unplug the flash drive from any network/computers to contain the virus.
- Scan with antivirus software – Plug the drive into a non-networked PC and scan it with updated antivirus software to identify and remove infections.
- Delete suspicious files – Manually delete any unusual files that weren’t removed by antivirus.
- Reformat the drive – If necessary, reformat the flash drive to completely wipe any residual viruses.
In severe cases where antivirus can’t remove the virus, reformatting gives you a clean slate. But be aware this will also delete all data on the drive, so make backups first.
Isolate the infected drive
The first priority is isolating the infected drive to prevent further spread. Don’t connect the flash drive to any other computers or networks.
Viruses can rapidly infect other devices in mere seconds. Physically unplug the flash drive from any PCs immediately if an infection is found.
Use antivirus software
Next, plug the infected drive into a non-networked, isolated PC. Don’t connect it to your main computer or networked machines or the virus could spread further.
A standalone laptop or secure computer works best for scanning. Install updated antivirus software and run a full scan of the flash drive.
This should detect and remove any viruses present. Follow up with additional antivirus scans to check the virus is fully eliminated.
Manually delete unknown files
In some cases antivirus software may miss infected files. As an added precaution, manually check the flash drive for suspicious unknown files that could harbor malware.
Look for random filenames, strange extensions, hidden system files or unusually large files. Permanently delete any dodgy looking items you find.
This helps remove any remnants left over that antivirus didn’t catch initially. Be very thorough checking the entire drive contents.
Reformat the flash drive
For severe infections that existing antivirus tools cannot remove, reformatting the flash drive may be necessary.
Reformatting completely erases all data and wipes the drive back to a fresh state. This removes even stubborn viruses that may be stuck on the drive.
On Windows, you can reformat using the full format option in Explorer. On Mac, reformat the drive via Disk Utility.
Make sure your files are backed up beforehand, as reformatting will wipe them! Once completed, you can restore your data with peace of mind the drive is clean.
Tips to avoid flash drive viruses
Following best practices helps keep your flash drive free from viruses:
- Don’t plug flash drives into public computers
- Disable autorun on the drive
- Set your antivirus to scan removable drives
- Avoid clicking on pop-ups or prompts from the flash drive
- Carefully check files before you copy them onto the drive
- Make sure you completely eject the drive before unplugging it
- Don’t use your flash drive to boot unknown computers
- Regularly back up important flash drive data
Flash drives are convenient for transferring files, but also carry risk of spreading viruses. Taking basic precautions like scanning with antivirus software, disabling autorun, avoiding suspicious files and properly ejecting the drive helps protect your computer and data.
Periodically reformatting your flash drive provides a thorough clean slate if it does become infected. Following secure usage practices gives you peace of mind using your flash drive safely and virus-free.