Can a virtual machine infect its host with a virus?

What is a virtual machine?

A virtual machine is a software emulation of a physical computer. It runs an OS and applications just like a physical machine, but the VM is managed by a hypervisor, a layer of software that allocates resources from the host computer -- CPU, memory and storage -- to the VM. Network segmentation controls the traffic between VMs and hosts, and each VM has its own virtualized hardware, meaning it does not interact with the host's physical hardware directly.

How can the host of a virtual machine become compromised?

Several vectors can cause the infection of VM hosts, despite the isolation. Here are some common attack vectors that can potentially lead to such infections.

Hypervisor vulnerabilities

The hypervisor is the software layer that manages VMs. If there are vulnerabilities in the hypervisor, attackers can exploit these to gain control over the host system. A hacker could exploit a vulnerability to execute arbitrary code on the host. Overreliance on the hypervisor's security might lead to neglecting other important security measures. While hypervisors are designed with security in mind, they are not infallible and can have vulnerabilities that attackers might exploit.

VM escape attacks

These are when attackers exploit vulnerabilities to break out of the VM's sandbox and execute code on the host. Although rare, VM escape attacks are possible. If an attacker can exploit a vulnerability in the hypervisor, they can break out of a VM and gain access to the host system, potentially compromising other VMs as well.

Shared resources exploitation

If a VM and a host system share resources, such as folders, network interfaces or clipboard, malware can use these shared channels to propagate. Users often enable shared folders for convenience, not realizing the security risks.

Misconfiguration

Security configurations in the hypervisor could be faulty in their composition, weakening isolation. For example, enabling unrestricted network access for a VM can expose the host system to network-based attacks.

Human error

Users might inadvertently transfer malware from a VM to the host system by copying infected files or using shared devices, like USB drives. Weak access controls can allow an attacker to utilize accounts that have higher privileges than they should.

Outdated systems

An unpatched or outdated hypervisor or VM OS with vulnerabilities increases the risk of these being exploited. Administrators might focus exclusively on securing VMs and neglect the host system's security.

Since the host is a critical part of the infrastructure, its compromise can have widespread consequences.

Hackers can exploit a vulnerability in a third-party management plugin for the hypervisor to gain access to the host.

Third-party tools and plugins

Hackers can exploit a vulnerability in a third-party management plugin for the hypervisor to gain access to the host.

The Virtualized Environment Neglected Operations Manipulation vulnerability in 2015 affected several virtualization platforms, including Xen, Kernel-based Virtual Machine and Quick Emulator. Because of VENOM, attackers could escape from a VM and execute arbitrary code on the host system by exploiting a flaw in the virtual floppy drive code.

Mitigation strategies to secure virtual machines and their hosts

By treating VM security best practices as an essential part of an overall cybersecurity framework, IT departments can protect their virtualized environments. This involves not just technical measures, but also strong policies, user education and continuous vigilance to detect and respond to potential threats.

To minimize the risk of VM escapes and host infections, organizations should follow and employ industry best practices.

Use security software

Deploy antivirus, intrusion detection and prevention, and other security systems on both VMs and the host. These tools can help detect and mitigate malicious activities.

Conduct regular updates and patching

Keep hypervisors, VMs and host systems up to date with the latest security patches and antivirus update definitions. Include virtualization management tools in the update schedule.

Employ network segmentation

Isolate VM networks from the host system's network. Use virtual LANs and firewalls to control and monitor traffic between VMs and the host. Isolate management interfaces from general network traffic to prevent unauthorized access.

Harden configurations

Follow security hardening guidelines provided by hypervisor vendors. Apply security best practices to harden the hypervisor, host OS and VM configurations. This includes disabling unnecessary services and using the principle of least privilege.

Limit or eliminate shared resources

Avoid or minimize the use of shared folders, clipboards and devices between VMs and the host. If necessary, use them with strict access controls and monitoring.

Use monitoring and logging

Implement continuous monitoring and logging for both VMs and the host system. Analyzing logs can help administrators detect suspicious activities early. Conduct regular security audits and vulnerability assessments of the virtualization environment.

Perform backups

Ensure that regular backups of both VMs and critical host configurations occur. Verify that backups are stored securely and tested regularly for recovery.

Limit third-party tools

Thoroughly vet any third-party tools or plugins for security before integrating them with the virtualization environment.

Educate users and administrators

Provide ongoing security training for users and administrators to raise awareness about potential threats, such as phishing attacks and social engineering. Enforce policies that dictate secure practices for accessing and managing the virtualization environment.

Helen Searle-Jones holds a group head of IT position in the manufacturing sector and has more than 25 years of experience with managing a wide range of Microsoft technologies in the cloud and on premises.