Network Security - Patch Management

Patch Management 

What it is (high level)
Patch management is the process of identifying, acquiring, testing, and applying software updates (“patches”) to operating systems, applications, and firmware. The goal is to close security vulnerabilities, fix bugs, and maintain performance and stability. In network security, timely patching is critical because unpatched systems are a leading cause of breaches and malware infections.

Why patch management matters

  • Closes security holes — attackers often exploit known vulnerabilities for which patches already exist.

  • Reduces attack surface — fewer weaknesses exposed to attackers.

  • Protects compliance — many frameworks (PCI DSS, HIPAA, ISO 27001) require timely patching.

  • Maintains reliability — patches often include stability and performance improvements.

  • Limits zero-day window — even if attackers discover new vulnerabilities, quick patching reduces exposure time.

Typical patch management cycle

  1. Inventory & monitoring

    • Track all hardware, OS, applications, libraries, and firmware.

    • Subscribe to vendor/security advisories (CVE feeds, vendor mailing lists).

  2. Assessment & prioritization

    • Evaluate severity (CVSS score, exploit availability, exposure to internet).

    • Prioritize critical security patches over cosmetic updates.

    • Consider asset criticality (servers vs. test machines).

  3. Testing

    • Apply patches first in a staging or test environment.

    • Validate compatibility with applications, integrations, and dependencies.

  4. Deployment

    • Schedule updates (balance security urgency vs. operational uptime).

    • Use automation tools (WSUS, SCCM, Ansible, Intune, etc.) for consistency.

  5. Verification

    • Confirm patches applied successfully (logs, reports, vulnerability scans).

  6. Documentation & reporting

    • Maintain records for compliance, audits, and troubleshooting.

Security challenges

  • Patch delays due to fear of downtime or breakage.

  • Shadow IT / unknown assets not included in the inventory.

  • Legacy systems no longer supported but still in use.

  • Large-scale environments with diverse OS/applications making uniform patching hard.

  • Third-party dependencies (plugins, libraries) that may lag behind vendor patch cycles.

Best practices for secure patch management

  • Maintain a full asset inventory — you can’t patch what you don’t know exists.

  • Prioritize critical vulnerabilities (remote code execution, public exploits).

  • Automate where possible — central patch management systems improve speed and consistency.

  • Standardize patch windows (e.g., monthly patch Tuesday, with exceptions for critical zero-days).

  • Use vulnerability scanning to validate patch status and detect missed systems.

  • Have a rollback plan in case patches break systems.

  • Segment and isolate unpatchable systems until they can be upgraded/replaced.

  • Train staff to understand the importance of patching and follow secure processes.

  • Include firmware and IoT devices in patch plans, not just OS and apps.

Detection & response angle

  • Vulnerability scanning (e.g., Nessus, OpenVAS, Qualys) to identify missing patches.

  • SIEM alerts for exploit attempts against unpatched systems.

  • Threat intelligence feeds to correlate unpatched CVEs with active exploits.

  • Incident response: if exploitation occurs, patch immediately, isolate compromised hosts, and investigate lateral movement.

Quick checklist for administrators

  • Maintain asset inventory.

  • Subscribe to vendor advisories / CVE feeds.

  • Prioritize patches based on severity + asset importance.

  • Test before production rollout.

  • Deploy patches via automated tools.

  • Verify & report compliance.

  • Handle exceptions (legacy/unpatchable systems) with compensating controls.

  • Regularly scan and audit patch status.