One of the biggest technological changes of our time is migration to the cloud. The fundamental element of this transformation is the virtual machine, which is a simulation of a physical computer executed with software. These virtual machines provide the agility, scalability and cost efficiency that define modern cloud computing. However, this same ability creates a thorny boundary to cybersecurity. The security of virtual machines is not a technical issue per se; it is a business requirement of any organization that functions in the cloud.
Virtual machine security in cloud computing refers to the policies, technologies, and controls that are implemented to protect confidentiality, integrity, and availability of the virtual machines and the data that they contain. The difference with this security model is that it goes beyond the traditional issues that were previously viewed as being part of one physical server. It should deal with a multi-layered environment where two or more customer virtual machines (also called tenants) are running on the same physical hardware, controlled by an abstract layer of software called the hypervisor.
This guide provides an in-depth analysis of the security of virtual machines. It breaks down the model of shared responsibility, examines the security levels bottom to top, and outlines the threats that are typical of virtualized environments. Above all, it presents a viable, practical framework of developing a strong security posture of cloud-based virtual machines, thus allowing organizations to reap the benefits of the cloud without jeopardising their safety.
The Concept of the Shared Responsibility Model
The blueprint of cloud security is the shared responsibility model. This paradigm outlines security responsibilities of the cloud service provider against those of the cloud customer. One of the most common and critical misconceptions is that all matters concerning security are handled by the provider. The fact is that the situation is subtler and requires prompt customer management.
Under an Infrastructure-as-a-Service model, the infrastructure cloud provider has the responsibility of securing the underlying cloud infrastructure, which includes the physical data centers, the networking fabric, and even the hypervisor itself. It is the responsibility of the provider to make sure that such a foundation is robust and isolated. The customer, however, is seen to be responsible in securing all that he or she has deployed on that infrastructure, such as the guest operating system that runs in the inside of this virtual machine, the applications installed on it, and the data stored in its virtual disks.
Inability to understand this segmentation of responsibilities is one of the main reasons that lead to security accidents in the cloud. The provider only sells a safe plot of land, but it is up to the customer to build a safe home on it, lock the doors, and handle access keys. This is the customer responsibility which is the heart of successful virtual-machine security.
The Hypervisor: Understanding Fundamentals
The software, known as the Virtual Machine Monitor, is the hypervisor which generates and executes virtual machines. It is the key to any virtualized system and it determines the access of physical resources to all virtual machines in a host like CPU, memory and storage facility. Its security is therefore the most important.
Breach of a hypervisor is a disastrous failure. This is because an attacker who attains control at the hypervisor level is likely to have the ability to monitor, modify or destroy all the virtual machines on that physical server. This is often referred to as a virtual-machine escape in which an attacker gains access to the isolation of a guest virtual machine and executes code on the hosting hypervisor layer. Such exploits are very advanced and uncommon, but their effects warrant the drastic efforts that cloud providers make to hypervisor harden them.
To protect this critical layer, providers use an assortment of minimized code bases, dedicated security teams, and regular independent audits. Trust but verify is your part as a customer. This requires choosing a provider that has an established track record, as well as has clear security policies, including publishing compliance certifications such as SOC 2 and ISO 27001.
Top Security threats to Virtual Machines
There are a great number of security risks that virtual machines are susceptible to. Others are known in the on-premise setting but others are specific to the shared nature of the cloud. Learning about these threats will be the initial step towards controlling them.
Insecure configuration is one of the threats that are most widespread. The simplicity of provisioning VMs may cause a phenomenon, referred to as VM sprawl where forgotten, unpatched machines may build up. These machines are often known to have default security settings, weak credentials, and unencrypted data that are easy to attack using automated attack methods.
Insider risk is another serious threat, and it can be either the provider based or the organization based. A bad provider administrator is very unlikely but a malicious provider administrator may have the potential access to your systems. More frequently, a privileged user that is not supposed to be in such a position in your company may accidentally or intentionally reveal sensitive information or set a service that is vital, out of place.
The noisy-neighbor attack is brought on by the multi-tenant quality of the cloud. Although such a performance problem, an attacker might have a workload that is set to saturate a shared physical resource, e.g. disk I/O or network bandwidth, thus impacting the performance of the other VMs on the host and essentially causing a denial-of-service situation.
More advanced attacks include malware and ransomware that are specifically designed to attack virtualized environments. This malware can spread extremely fast between interconnected virtual machines and can also attempt to exploit vulnerabilities in virtual hardware or management interfaces. Finally, data breaches remain the most significant issue be it caused by external intrusion of data or insider theft or just accidental disclosures of data stored on under-secured virtual disks.
Building a Robust VM Security Posture: A Multi-Layered Strategy
The threat of these attacks requires a threat to defense-in-depth. The plan consists in placing many, intersecting layers of security measures to the extent that in case one layer collapses, the other still offers security.
Identity and Access Control
The foundation of cloud security is Identity and Access Management. In a virtual environment the least privilege and the principle of least privilege should be taken seriously. This involves making users and services gain access to the minimum of granting them permissions to perform their respective work, and no more.
A programmer will not need root access to a production virtual machine. Similarly, a database administrator would not need to be able to make new virtual networks. Role based access control is a must-have in order to handle these permissions on a large scale. In addition, strong authentication should be carried out on each access request.
All user accounts including those with high privileges should be required to have multi-factor authentication. Where system-system communication is required, as is the case with a web server and a database virtual machine, passwords should be replaced with API keys or better still short-lived certificates to establish machine identity. The regular application of these IAM policies also significantly reduces the attack surface by eliminating over-authorized accounts, which are one of the key targets that attackers use.
Hardening the Virtual Machine
A virtual machine should be treated in terms of security as a physical server. Such a process of protecting the guest operating system and its applications is called hardening. This process starts with the implementation of a standardized and minimal image. Before the VM is deployed, superfluous user accounts, services, and software should be removed, thus minimizing its footprint and the possible amount of vulnerabilities.
All the applications installed along with the operating system should be updated with the latest security patches. In an active cloud platform, it is not possible to manually patch. There should be an automated patch-management plan in place that may require the use of cloud-native or a third-party service to scan the virtual machines on a regular basis to ensure that they have the appropriate patches and apply updates to them based on the specific timeline.
Moreover, host based security controls are important. The firewall of the host should be set up in a way that prevents all unnecessary inbound and outbound traffic in the network. Antivirus or anti-malware software is recommended to be installed and kept up to date in order to provide protection against known threats. Lastly, file-integrity monitoring can also be installed to look at any unauthorized changes to important system files, which will give an early warning that the system has been compromised.
VMware Network Security
The network in the cloud is a software-defined entity which provides strong security features that should be used. The virtual network is the first line of defense; every workload is supposed to be placed in its own virtual network or subnet, and thus different levels of an application system, e.g. web servers, application logic, databases, etc, are isolated.
Network security groups or access control lists should be strictly used to control communication between these segments. A web server must also be allowed only to communicate with the application server on specific ports and the database should only be allowed to accept a connection only to the application server. This process is referred to as micro-segmentation and includes any possible breach and it prevents a lateral movement by an attacker.
Any information being sent between virtual machines, especially over different networks, or to on-premises data centers, should be encrypted when being transferred. This is normally done through using Virtual Private Networks or TLS encryption. In the case of management ties like Remote Desktop Protocol or Secure Shell, they should not have direct access to the outside world wide web. Rather, use a bastion host or jump box, providing a single highly fortified point of administrative access.
Data Protection Strategies
The ultimate goal is to provide a security of the information stored in your virtual machines. The best way of having confidentiality is through encryption. Encryption of sensitive data at rest should be done which involves encryption of the virtual hard disks holding the operating system and data of the VM.
Cloud systems offer easy-to-use alternatives to this, and may make use of managed keys attached to your account. To have the best amount of control, you can use customer-controlled keys, and thus, the encryption keys are held in exclusive possession. A strong data backup and disaster recovery plan should also be put in place.
Your virtual machines should also be backed up automatically on a regular basis and stored in a secondary location. The backups should also be encrypted, and the integrity of the same should be checked by performing periodical restoration tests. The last compensation of the defense against data corruption, ransomware, and accidental deletion is a rigorously tested backup.
Incidences Response, Log and Monitor
It is impossible to defend what you do not see. Detecting and responding to security incidents is impossible without comprehensive monitoring and logging. You need to achieve total transparency of the operations in and around your virtual machines.
The process is based on the collection and analysis of logs of the guest operating system, application logs, and, most importantly, cloud audit logs. These audit logs record all API calls done against cloud resources, the initiator, the source location and the action performed. These records are priceless in terms of forensic analysis.
To centralise these logs and correlate the events across the whole environment a Security Information and Event Management system should be deployed. Alerts should be set on suspicious actions, e.g. when attempts to log in have failed and were made under odd locations, new administrative users are created or when extensive and significant transfers of data are made. A properly documented incident response plan will mean that once an alert is given, the team knows exactly how to contain, eliminate, and recover the threat in time and effectively.
The Human factor in VM Security
A virtual environment cannot be secured with the help of technology. A decisive role is played by human operators, administrators and developers. Even a well-built technological defence may fall when it is compromised by a single social-engineering attack or an accidental mistake of a poorly trained member of the team in terms of configuration. In turn, the overall security strategy should include a people and processes focus.
Security awareness training is not an ornamental aspect but it is a high control. The members of a team need to be educated to identify the presence of phishing attacks, which are often the starting point of a breach. They should understand the first and the most important value of a strong and unique password and the need to have multi-factor authentication. Moreover, system administrators and developers will need training in the basics of cloud-security. They have to know how to use the cloud-management console safely and the implication of the services they offer.
The Input of Automation and DevSecOps
Rudimentary checks of security are too sluggish and are prone to laxation in a dynamic cloud structure. The intensity and rate of deploying virtual-machines requires an automated security method. It is against this that the principles DevSecOps (development, security, and operations) take center-stage. Security is to be part of the development and deployment pipeline – a notion frequently known as a shift-left.
Infrastructure-as-Code tools (e.g. Terraform or AWS CloudFormation) allow defining and provisioning VMs as a declaration in a code file. Security misconfigurations before deployment of these templates should be scanned. Compliance with security policies can be imposed with automated scanning, where all VM are built with encryption turned on, all unnecessary ports are closed, and suitable tags are added on them.
Summary
Security of virtual-machines in cloud computing is not a project that has an endpoint. It entails a cyclic process of measurement, application, surveillance and enhancement. The threat environment is continuously changing; therefore, it needs defense to adapt accordingly. With the adoption of a shared responsibility model and a multi-layered approach to security (that covers identity management, system hardening, network segmentation, data encryption, and active monitoring) an organization can develop a robust security stance.
This would be the way to allow an organisation to fully leverage the enormous amounts of power and flexibility of virtual machines in the cloud with a lot of assurance. Digital assets can be used safely because a strong, modern and active security system can be trusted to protect them. Innovation and growth can continue. This is not to achieve the impossible goal of ultimate security but to handle risk in a competent manner that makes systems a hardened target and the agility offered by the cloud to be maintained.
