CTDISR-2025 Section 19 mandates a regular vulnerability assessment cadence, CVSS-based prioritisation of findings, and documented remediation tracking. For most Pakistani ISPs, this means building a vulnerability management programme from near zero: scanning has either never been done systematically or has been done once for a specific purpose without establishing an ongoing programme.

A vulnerability assessment programme is not a one-time engagement. It is a continuous cycle of scanning, prioritising findings, remediating, and verifying remediation. The evidence auditors look for is not a scan report: it is a pattern of regular scanning, documented remediation actions against findings, and verification that high-severity findings were addressed within the required timeframe.

Scope Definition

The first decision is what to scan. For CTDISR-2025 compliance, the scope should include all internet-facing infrastructure (routers, switches, servers, management interfaces with any public accessibility), internal management infrastructure (NMS platforms, RADIUS servers, billing systems), and endpoint devices used by staff to manage operational systems.

For ISPs specifically, the highest priority scope items are: the management interfaces of edge and aggregation routers (most likely to have unpatched vulnerabilities that are directly internet-accessible), the RADIUS and billing servers (hold subscriber data, credentials, and financial information), and any web-facing subscriber portals or APIs.

Scanning Tools

The scanning tools available range from open-source options adequate for compliance baseline scanning to commercial platforms with broader coverage and better reporting.

OpenVAS/Greenbone is the most capable open-source vulnerability scanner and covers the core use case for most Pakistani ISPs. It is self-hosted, free to use, and has a comprehensive plugin library covering common network equipment and server software. The management interface (Greenbone Security Assistant) provides reporting in formats that can be included in CTDISR evidence packages. The operational overhead of maintaining an OpenVAS deployment is real but manageable for an ISP with Linux administration capability.

Nessus Essentials is the free tier of Tenable's Nessus scanner, limited to 16 IP addresses per scan. For smaller ISPs focusing initial scanning on the most critical infrastructure, this limit is workable. The paid Nessus Professional tier removes this limitation and adds more comprehensive reporting.

Nuclei is a fast, template-based scanner useful for specific vulnerability classes (web application vulnerabilities, known CVEs, misconfigurations) and complements OpenVAS for web-facing assets rather than replacing it.

Assessment Cadence

CTDISR-2025 does not specify an exact scanning frequency, but quarterly vulnerability assessments of internet-facing infrastructure are the industry standard and what auditors expect to see in evidence. Internal infrastructure scanning can be less frequent, semi-annual, as long as critical findings from each scan are remediated before the next.

Beyond scheduled assessments, configure your vulnerability scanner to run targeted scans whenever significant changes are made to infrastructure: a new service deployed, a network device added or reconfigured, a major firmware update applied. Change-triggered scanning catches vulnerabilities introduced by specific changes before they become established exposures.

CVSS Prioritisation

CTDISR-2025 Section 19 specifically requires CVSS-based prioritisation of findings. CVSS (Common Vulnerability Scoring System) scores vulnerabilities from 0 to 10, with scores above 9 classified as Critical, 7-8.9 as High, 4-6.9 as Medium, and below 4 as Low.

Your remediation timelines should be tied to CVSS severity: Critical findings require remediation within 7-14 days, High within 30 days, Medium within 90 days, and Low addressed in the next scheduled maintenance cycle. These timelines should be documented in your vulnerability management policy so the evidence shows that your timelines are defined and being followed, not just that you are remediating when convenient.

Remediation Tracking and Evidence

The most common gap in vulnerability management programmes is remediation tracking. Scanning produces findings, some are remediated, some are not, and there is no systematic record of what was done and when. An auditor reviewing Section 19 compliance needs to see: the scan reports, the remediation actions taken against findings, evidence of the remediation (configuration change records, patch version confirmation), and verification scans confirming findings are closed.

Use a tracking document or your compliance management platform to record each significant finding from each scan cycle, the assigned severity, the remediation action taken and by whom, the completion date, and the verification scan result. ComplianceIQ manages this evidence alongside all other CTDISR sections.

For hands-on vulnerability assessment and remediation support, Cybersecurity for ISPs conducts assessments and manages the remediation programme as a service engagement. For a scored view of your Section 19 posture alongside the full 104 CTDISR controls, ISP Audit provides the gap assessment before the external auditor does.