Can a Virus Escape a Virtual Machine?

There’s no doubt that computer viruses are fascinating. Whether you’re looking to use a virtual machine just to visit that one risky website or to do full-blown malware analysis, it’s hard not to wonder whether using a virtual machine is actually protecting your computer from viruses.

While it isn’t common, there are ways for viruses to escape from virtual machines. If the VM is connected to your home network, they can often spread across it. Many viruses can also use vulnerabilities like x86 virtualization and the virtual COM ports.

In this article, I’ll explain the risks you need to be aware of when running an infected virtual machine and the most common vulnerabilities viruses use to escape.

I’ll also explain the best techniques you can use to reduce the likelihood of a virus escaping.

How a Virus Might Escape a Virtual Machine and Infect the Host Operating System

Viruses can escape a virtual machine by exploiting features that connect the virtual machine to the host machine or other environments, such as a shared home network or even shared clipboard features. 

Viruses Can Spread Across the Network

The most common vulnerability that viruses use to escape virtual machines is spreading across the network.

Many viruses are already made to spread across networks, so if you have your virtual machine connected to your router, they won’t have any trouble spreading. 

How To Prevent VM Virus From Spreading Across the Network

• Make sure that your virtual machine is completely disconnected from the Internet. If the virtual machine has previously connected to networks, you should make sure to have the VM ‘forget’ them.
• Disable or turn off sharing for all of your serial and USB ports. You can disable access to USB and serial ports by navigating to the settings of your virtual machine and disabling the USB and serial controllers. Most virtual machine applications also offer settings to disable USB and serial port access.
• Disable file and printer sharing on your host machine. Certain viruses are known to exploit the file and printer sharing network feature. You can disable file and printer sharing on Windows computers by navigating to Settings > Control Panel > Network and Internet > View network status and tasks > Change advanced sharing settings > Turn off file and printer sharing. 
• If you need to connect to the internet, use a wireless hotspot. If you connect your virtual machine to your usual home network, you’re exposing all of your other devices to viruses. By tethering your virtual machine to a hotspot, you have the option of turning off the hotspot and eliminating internet access at any time.

Viruses Can Spread Across Shared File Systems

Another way that viruses can spread between virtual machines and their hosts is when files are shared.

If you move files from your virtual machine to your host machine, viruses may be able to travel along without you noticing.

Features that employ file sharing, like shared clipboard, are also capable of spreading viruses between your virtual machine and host machine. 

How To Prevent VM Virus From Spreading Across Shared File Systems

• Disable folder sharing. If you want to keep your host machine safe from viruses, you shouldn’t have any shared files. A great way to start is by disabling folder sharing. Most virtual machine software supports this. In VMware, you can disable folder sharing by going to VM > Settings > Options > Shared Folders and turning the feature off.
• Disable drag-and-drop. Since the drag-and-drop feature connects the virtual machine to the host machine, it is an area that hackers could potentially exploit. You can disable drag-and-drop in VMware by navigating to VM > Settings > Options > Guest Isolation and turning the drag-and-drop feature off.
• Disable shared clipboard. While the shared clipboard feature is enabled by default in most virtual machine applications, it’s easy to disable. You can disable shared clipboard by navigating to VM > Settings > Options > Guest Isolation and turning the ‘enable copy and paste’ feature off.

Is It Easy for Viruses To Escape From a Virtual Machine?

Generally speaking, it’s very difficult for viruses to escape from a virtual machine. Most VM vulnerabilities are exploited to infiltrate valuable targets, like a government office or hospital network. Since it’s so difficult, you’re unlikely to be a target, but staying safe is essential.

The reason why it’s so difficult for viruses to escape from virtual machines is that the software has become extremely sophisticated.

While older versions of VirtualBox and other software have known vulnerabilities, the recent releases of these programs are generally understood to be extremely secure.

Even when viruses are capable of understanding they’re inside a virtual machine, they’re unlikely to attempt to escape.

Most viruses that can detect virtual machines self-destruct upon detection to prevent malware experts from analyzing them.

Since legitimate exploits are so hard to find, they’re generally reserved for high-profile attacks.

Most of the vulnerabilities hackers use to exploit virtual machines take advantage of the connection between the virtual machine and the host computer.

If the virtual machine is connected to your real home network, for example, many viruses will opt to use the home network to spread.

Other viruses have been known to use avenues like cache side-channel attacks to access information about the host OS.

What Happens When a Virus Escapes From a Virtual Machine?

Unfortunately, if a virus can escape from a virtual machine, it can quickly cause serious harm to your computer. Aside from the risk of sensitive data like your financial information or passwords being stolen, viruses can also damage your computer’s operating system and hardware. 

There are a lot of ways that viruses have been known to escape from virtual machines and cause damage.

When a virtual machine is installed directly over the operating system, it leaves tons of attack surfaces open, including network access, guest additions, shared filesystems, peripherals access, shared copy/paste buffers, and unified desktop features. 

It’s possible to mitigate the potential damages by setting up your virtual machine securely.

Ideally, the virtual machine should be isolated from your home network and any devices that you regularly use.

You can even run the virtual machine on a bootable USB drive on a burner computer to ensure it has almost zero access to anything valuable. 

In the end, it doesn’t take a strong virus to cause hundreds and even thousands of dollars of damage.

You can save yourself a significant amount of money and grief by taking the right precautions to configure your virtual machine.

How To Make a Secure Malware Analysis VM

While it’s impossible to completely prevent viruses from infecting your computer or network, especially when you allow them to infect a virtual machine, there are ways to reduce the likelihood of them spreading.

Despite the clear occupational risk, malware analysis experts regularly allow malware to infect their virtual machines with little to no consequence.

1. Configure the Basic Specifications of Your Virtual Machine

To start, you’ll need to pick a hypervisor (also known as virtual machine software) to run your virtual machine on.

VMware Workstation Pro, KVM, and VirtualBox are the best software for general use. VirtualBox is particularly good for beginners since it’s free to use while still offering the same essential features (like snapshots). 

Once you’ve chosen your hypervisor, you’ll need to decide on the specifications of your new virtual machine.

If possible, you can stick to the recommended amount of RAM but should consider using more than one CPU core.

If you’re using only a portion of your CPU cores, you can set the execution cap to 100%, but if you’re using all of your CPU cores, you should set it lower to avoid freezing your computer.

If you need to access the Internet, you should set your networking settings to “NAT”.

This is the best overall option you can choose since it insulates the other devices on your host network from your virtual machine while still providing the same Internet access.

You don’t need to adjust any other features unless you have a specific reason to do so. 

2. Install Your Windows Virtual Machine

Once you’ve configured the basic specifications of your virtual machine, you’ll need to start working on the operating system installation.

While you’ll need to purchase a valid software key, you can find all of the available versions of Windows here. 

Once you’ve downloaded the Windows ISO of your choice, you can add it to the virtual machine by navigating to Settings > Storage and finding the ‘Empty’ storage device.

Click ‘Empty’ to view its attributes, then click on the CD icon next to the Optical Drive selector to open File Explorer.

Once File Explorer has opened, you can find your ISO and select it. Click ‘OK’ to confirm the selection.

Next, you’ll need to boot the virtual machine. As it boots the Windows ISO, you’ll need to answer basic setup prompts.

Make sure that you don’t activate Windows since many viruses are capable of stealing product keys. Don’t install Guest Additions, either, since many viruses can use this as an attack point.

3. Prepare Your Windows Virtual Machine for Malware Analysis

When Windows is finished installing, you’ll still need to take a few extra steps before your virtual machine is ready for malware analysis.

You should start by taking a snapshot of the virtual machine since this will give you a point to revert back to if anything goes wrong. You can take a snapshot by navigating to Machine > Take Snapshot.

Next, you should ensure that your host machine and any other devices on the network are adequately protected from any potential viruses.

You should verify that every device has an antivirus program installed. The antivirus program should be completely up-to-date.

Ensure that features like your computer’s firewall and active malware scanning are enabled.

Finally, you’ll need to install any of the software you want to use with your malware — and to find the malware itself!

It’s important to note that you should always maintain good cybersecurity practices when you’re using your virtual machine.

Even if you took care to install your virtual machine correctly, it only takes one absentminded mistake to give viruses a vector to spread.

4. Maintain Best Practices To Defend Your Host Machine From Malware

To prevent viruses from escaping from your virtual machine, you need to make sure that you’re always using your virtual machine in a safe way.

Here are some of the best practices you can use to defend your host machine and reduce the likelihood of any viruses escaping from your virtual machine.

• Avoid plugging USB devices into your virtual machine. If possible, you should disable the USB and serial port features entirely. As mentioned before, one of the most common ways that viruses are able to escape from virtual machines onto host machines is through shared files — and USB devices represent a direct avenue to spread.
• Never run viruses on a virtual machine while it’s connected to the Internet. It’s not just viruses infecting your host machine you have to worry about when you’re working with them on a virtual system. If they run from your network, your virtual machine can be used as the host for serious digital crimes.
• Avoid putting any secure files on your virtual machine. Anything on your virtual machine is easy for hackers to access. If you plan to work with viruses on a virtual machine, then, you should avoid logging into your bank account or saving any private documents.
• Don’t use features like shared folders, shared drag-and-drop, or shared clipboard. These features link the host machine to the virtual machine, and create potential attack surfaces that viruses can use to spread.
• If you want to run a VPN, run it on your host machine. If you run it inside the virtual machine, it’s incredibly easy for hackers to bypass. They won’t have the same ability to interfere with your VPN when you run it from the host machine.

Final Thoughts

Whether you’re interested in studying viruses or just want to open a suspicious file, there are a lot of reasons why virtual machines might seem useful.

When it comes to dangerous computer viruses, however, it’s hard not to wonder if they are able to break through a virtual machine and infect your computer.

Unfortunately, it is possible for viruses to escape a virtual machine and harm your computer.

As long as you configure your virtual machine correctly and use good cybersecurity practices, though, the risk of a virus escaping your virtual machine is negligible.