- How patch scanning works
- The scanning step in your patching workflow
- Agent-based vs. agentless patch scanning
- What does a patch scan check?
- How often should you run patch scans?
- Common patch scanning challenges
- Best practices for patch scanning
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A clock starts every time a software vendor publishes a security fix. On one side, your IT team works to test and deploy the update. On the other hand, attackers probe for unpatched systems. Patch scanning tells you which of your endpoints have fallen behind.
Without a scan, you are relying on assumptions about your patch coverage. With a patch scan, you get a verified, endpoint-by-endpoint report of what is missing and what is exposed.
A patch scan runs against every managed endpoint—servers, workstations, and laptops—comparing installed software with a vulnerability database to flag missing patches, outdated versions, and exposed systems. It is the detection layer of the patch management process, and without it, every other step runs blind.
According to Verizon's 2026 Data Breach Investigations Report, vulnerability exploitation rose 55% year over year to become the leading breach entry point for the first time in the report's 19-year history. Patch scanning is how you spot those gaps before an attacker does.
How patch scanning works
A patch scan compares the current state of software on each endpoint against a known database of available patches. The process typically follows three steps.
First, the patch management server synchronizes with an external vulnerability database. This database contains information about newly released patches from vendors like Microsoft, Adobe, Oracle, Apple, and others. It maps each patch to the specific vulnerability it addresses, the affected software versions, and the severity rating.
Second, scanning agents or remote probes check each endpoint in your network. They read installed software versions, applied updates, registry entries (on Windows), and package manifests (on Linux). The agent then compares what is installed against what should be installed based on the vulnerability database.
Third, each agent sends its results back to a central console. You get a clear picture of which systems are missing which patches, broken down by severity, OS, application, and endpoint group. This data feeds directly into your prioritization and deployment workflow.
The entire cycle can run in the background without disrupting users, and most organizations configure it to repeat on a fixed schedule.
The scanning step in your patching workflow
Scanning connects asset discovery (knowing what devices and software you manage) to patch prioritization (deciding which missing patches to address first). If you skip scanning, you are guessing which systems need patches instead of working from verified data.
Scan results also feed directly into compliance reporting. Frameworks like PCI DSS, HIPAA, SOC 2, and ISO/IEC 27001 all require organizations to identify and remediate known vulnerabilities on a defined cadence. A scheduled patch scan with logged results and timestamps gives auditors the documented evidence they need.
Agent-based vs. agentless patch scanning
There are two main approaches to scanning, and the right choice depends on your environment.
Agent-based scanning places a dedicated software component on each managed machine. The agent runs locally, checks the system's patch status, and reports back to the central server. This approach works well for remote endpoints and laptops that connect to the corporate network intermittently. The agent can scan off-site and sync results when connectivity returns because it lives on the machine. It also removes the need for admin credentials to be passed across the network during each scan.
Agentless scanning relies on remote connections from a central server. The server authenticates to each endpoint over the network (using protocols like WMI on Windows or SSH on Linux) and pulls patch status data remotely. This approach is faster to set up since there is nothing to install on individual machines. However, it requires network connectivity and open ports between the scanning server and every target, which becomes a limitation in distributed environments.
ManageEngine Patch Manager Plus uses an agent-based approach. The agent installs once, handles scanning and deployment, and eliminates the network dependency that makes agent-less scanning fragile at scale.
What does a patch scan check?
A scan covers more than just OS updates. A thorough scan examines four categories across your endpoints.
Operating system patches include cumulative updates, security updates, and hotfixes for Windows, macOS, and Linux distributions. On Windows, this covers Patch Tuesday releases and out-of-band updates. On Linux, it checks distribution-specific repositories (Red Hat, Ubuntu, SUSE, and others) for kernel patches and package updates.
Third-party application patches cover software from vendors other than the OS maker. Applications like Adobe Acrobat, Google Chrome, Mozilla Firefox, Zoom, Java, and hundreds of others each release their own patches on their own schedules. These are easy to miss without automated scanning, and they account for a large share of exploitable vulnerabilities. According to Google’s Threat Intelligence Group, 90 zero-day vulnerabilities were exploited in the wild in 2025, and 48% of them targeted enterprise software.
Firmware and driver updates include BIOS updates, chipset drivers, and peripheral firmware. These are less frequent but can carry high-severity vulnerabilities.
Antivirus definition updates are technically not patches, but many patch management tools include them in the scan scope. Outdated definitions leave endpoints blind to new malware signatures.
The scan cross-references all of this against vendor-maintained vulnerability databases to flag which missing patches correspond to actively exploited threats.
How often should you run patch scans?
Scan frequency depends on your risk tolerance, the size of your environment, and your compliance requirements.
Daily scanning is the baseline for most organizations. Running a scan once per day, typically after the patch database synchronizes with vendor sources, catches new vulnerabilities within 24 hours of disclosure. If you align your scans with Microsoft's Patch Tuesday cycle, schedule the first post-release scan for Wednesday or Thursday. Microsoft occasionally pulls back problematic patches within the first day or two, so a short delay gives you a buffer.
Continuous or on-demand scanning is appropriate for internet-facing servers and systems processing sensitive data. The Verizon 2026 DBIR found that attackers now exploit known vulnerabilities within hours of disclosure, making real-time detection critical for high-value assets. Some tools trigger a scan automatically whenever the vulnerability database updates or whenever an endpoint reconnects after being offline.
Weekly scanning may work for lower-risk internal systems, but this cadence introduces gaps. If a critical vulnerability is disclosed on a Monday and you do not scan until Friday, that is four days of blind exposure.
For guidance on fitting scan cadence into a broader patching workflow, see our patch management best practices.
Common patch scanning challenges
Even a well-configured scanning setup runs into friction. These are the issues that trip up most IT teams.
Remote and intermittently connected endpoints are the biggest challenge in hybrid work environments. A laptop that was offline during the scheduled scan window will show stale data in your console until it reconnects and completes a scan. Agent-based tools handle this better, since the agent queues the scan locally and syncs when connectivity returns.
Legacy operating systems that vendors no longer support will not have new patches to scan for, but they still carry known vulnerabilities. Your scan results may show these systems as compliant simply because no patches are available, which masks real risk. Flag end-of-life systems separately and apply compensating controls.
Third-party application coverage gaps appear when your scanning tool does not track a specific application. If your team uses niche or internally developed software, you may need to supplement automated scans with manual checks for those packages.
Best practices for patch scanning
Getting value from patch scanning comes down to consistency and coverage.
Start by making sure your asset inventory is complete and current. A scan is only as good as the list of endpoints it covers. Use automated discovery to catch new devices as they join the network. If a device is not in your scope, it is not being scanned, and an unscanned endpoint is an unpatched endpoint.
Automate your scan schedule and tie it to your patch database synchronization. A scan should follow automatically when the vulnerability database updates. This removes the manual step and shortens the window between patch availability and detection.
Review scan results promptly. A scan that runs daily but sits unreviewed for a week is not helping you. Route critical findings directly into your deployment queue and assign clear ownership for remediation.
Do not treat scans as a one-time event. After you deploy patches, rescan to verify that the installations succeeded and that no new gaps have appeared. This post-deployment validation step is often skipped, but it is the only way to confirm that your endpoints are actually protected.
Finally, make sure your scanning tool covers your full software stack. OS patches alone are not enough. Third-party applications are a frequent entry point for attackers, and security patching across all of them requires a tool that supports broad application coverage.
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