A guide to operating system patching

Operating systems (OSs) form the foundation of any network, acting as the interface between users, hardware, and software. This is why operating systems are one of the top targets in a network, with hackers looking to exploit any vulnerability present. To maintain a secure and stable operating system layer, consistent and proactive operating system patching practices are essential.

This is not a one-time activity but a continuous process known as operating system patching.

What is operating system patching?

In addition to operating system patches, which are targeted and frequent, vendors also bundle and release a bunch of fixes and enhancements that are less frequent, called operating system updates.

And finally, there are the operating system upgrades that introduce a new major version of the operating system, changing the architecture, features available, and user interface. These are rare and significantly overhaul the operating system. For example, an operating system upgrade from Windows 10 to Windows 11.

To better understand how each of these three operating system maintenance approaches works, the following section summarizes the key differences between them.

Difference between operating system patching, updates, and upgrades

Operating system patching in IT patch management

The process of patch management covers a wide range of components like third-party applications, firmware, drivers, network devices, and operating systems. Of all this, operating system patching sits at the core, as operating systems form the base on which other components are built.

A security vulnerability at the operating system level can have far-reaching consequences compared to other components. Once the operating system is compromised, all the other components built on the operating system are also at risk, which is why it's considered the highest-priority layer and governed with the strictest SLAs and escalations.

To better understand why operating system patching carries this level of criticality, it helps to look at how operating system changes are structured at the code level.

Anatomy of operating system changes

Operating system patching

If we drill an operating system patch down to its core, it is nothing but small chunks of object code targeted to fix very specific and urgent problems like security fixes, bug fixes, and functionality improvements.

As these are targeted to edit specific files and directories, they are usually smaller and more frequent than major upgrades. For example, if there is an urgent security vulnerability present in the operating system, the operating system patch is deployed to secure the vulnerability without disrupting the whole operating system.

Operating system updates

At the code level, operating system updates come packaged with operating system patches. They target a combination of improvements, including:

• Stability improvements: Fix system crashes and unexpected behavior reported by users, vendors, and internal tests.
• Performance optimizations: Targeted to improve multiple system performance factors like boot time, memory management, power, and background process efficiency.
• Minor feature enhancements: Incremental feature improvements in usability, configuration, and tools without affecting the overall operating system design.
• Dependency and compatibility updates: Updates to libraries and drivers to ensure compatibility with the latest applications and hardware.
• Security patches: A cumulative package to address both previously released and newly released security fixes that can bring a system up to date in a single update.

As these are designed to address a wider set of components, they are less frequent than operating system patches and are released monthly or quarterly.

Operating system upgrades

An operating system upgrade often introduces an entire code branch created by the respective vendor. It does not modify existing code in place but replaces it with newly developed code to bring about major changes in the operating system. These include changes in components like:

• Kernel and kernel modules
• System files and services
• Core libraries
• Device drivers
• Firmware interfaces

Owing to the transformational nature of an operating system upgrade, it is released rarely (once every several years) compared to a patches and updates.

Why do some operating system patches require reboots while others don't

Simply put, a reboot is required when the patch makes changes to components that are actively used or cannot be updated when the system is running. Some examples of these critical components include kernels, core system libraries, and low-level drivers.

These components are running from system boot to shutdown, and the updated code can take effect only after the system restarts. Hence most of the patches for these components require machine reboot.

What happens when operating system patches are ignored

Failing to patch operating systems often leads to business disruption caused by security breaches/operational outages, which is why operating system patching must be a streamlined and continuous process. This section takes a closer look at the impact of unpatched operating systems.

Vulnerability exploitation: The obvious impact of an unpatched operating system is vulnerability exploitation, as the vulnerabilities are publicly disclosed and become an easy target for threat actors.

Performance issues: Operating system patches are also used to fix non-security performance issues like system crashes and memory drain. If the patches are not applied on time, these issues can result in slow performance, application failures, unexpected reboots, and more.

Business impact: If a vulnerability is exploited due to an unpatched operating system, it will result in operational downtime, financial costs, and reputational costs. Performance issues like frequent system crashes, system slowness, unresponsive machines, and application failures during peak hours can severely affect the reliability and productivity of an organization.

Non-compliance: When left unpatched, operating systems can become non-compliant according to major regulatory frameworks (the PCI DSS, ISO 27001, HIPAA, etc.) as they have to be patched within predefined timelines.

Operating system patching challenges across environments

End-user devices

The sheer number of laptops and desktops in an organization, coupled with the different operating system types and versions, often complicates operating system patch deployment. The amount of time and effort required to do this manually can be significant, leaving the IT team with little to no time to focus on other high-value tasks.

Even when patch management software is used to automate the operating system patch deployment process, users can still postpone system reboots, shut down devices during deployment, or work across time zones causing delays and operational complexity.

Solution: Having a comprehensive asset and operating system inventory and an automated patch deployment tool can easily solve the problems caused by the number of endpoints, the variety of operating system flavors, and multiple time zones. To avoid user interference, patches with strict deadlines can be deployed when the individual systems are idle.

Servers

With organizations often using servers to support their business-critical applications, operational downtime due to service restarts and system reboots is unacceptable. There is also the risk of a patch outage, as some patches might behave unexpectedly after deployment. Prior experience of patch outages in critical servers might make organizations think twice before operating system patching, even to fix security threats.

Solution: Testing the operating system patches in a representative subset of systems before full deployment will help detect potential issues (if present) early. After thorough testing and ensuring complete confidence in the success rates, the server operating system patches can be rolled out in a phased manner to minimize downtime risk, ensuring business continuity.

Remote and hybrid systems

With remote work becoming the new norm for many organizations (at least partially), the number of devices outside the company network has increased significantly. The most practical way to reach these devices is to connect over the internet, which can be hard to achieve manually, or use an automation tool that requires the devices to connect to the company network.

Even if the devices can connect over the internet, they are then at the mercy of available connectivity and bandwidth, making it difficult for IT teams to download and deploy operating system patches. Inconsistent internet access can still be a problem for devices online, often causing patch downloads to fail.

Solution: A cloud-based patch management solution can help identify new patches, collect them, and deploy operating system patches to devices outside the company network. Using these tools, the deployment status of the operating system patches must be consistently monitored, and the failed patches must be automatically reattempted.

Bandwidth throttling and patch scheduling when individual machines are idle can help address the problems caused by low bandwidth.

Air-gapped or restricted networks

Organizations with a closed network have an added bottleneck in operating system patching, as endpoint and server operating systems are isolated from the network. This creates a unique patching challenge where the operating system patches must be manually downloaded, tested, and then sent to an external device, which can be a CD, USB, or internal repository.

When operating system patching is a manual process, it increases the time and effort required, and often makes the whole process error-prone.

Solution: Organizations must have a streamlined process for transferring the operating system patches to the internal repository, and the repository must regularly be updated. Leverage automation to deploy and monitor operating system patches within the closed network wherever possible to speed up deployment and reduce errors.

Many of the problems discussed above can be solved with the help of a comprehensive operating system patch automation solution. The next section will dive deep into the factors that make a patch automation solution stand out from a manual operating system patching process.

How mature operating system patching really works

Organizations that leverage automated patch management solutions that offer consistency, risk assessment, and seamless patch delivery can be said to have operating system patching maturity. This will help them ensure system security, process stability, and compliance without interrupting daily business operations.

The following section will break down the key factors that make up a mature operating system patching process.

• Continuous visibility: Complete and up-to-date visibility into devices, servers, operating system types, versions, and patch status.
• Risk-based prioritization: Patch deployment prioritization based on patch severity and asset criticality.
• SLA-based frequency: Defined SLAs for patch remediation based on operating system patch criticality and ensuring the operating system patches are deployed on agreed timelines.
• Smart classification: Patch deployment based on reboot requirements.
• Controlled testing: Patch testing on a representative subset of the network for stability, compatibility, and performance.
• Phased deployment: Automated deployment incrementally to minimize risk.
• Recovery planning: Continuous monitoring to redeploy failed patches.
• Reporting and compliance: Generate audit-ready reports for compliance requirements.