How to remediate – Service Detection (2nd Pass)

1. Introduction

The Service Detection (2nd Pass) vulnerability is a plugin that identifies common network services which may have been missed during initial scans due to temporary network issues. This matters because undetected services can present attack vectors for malicious actors. Systems usually affected are those with open ports and running network applications, potentially impacting confidentiality, integrity, and availability if exploited.

2. Technical Explanation

This plugin complements the find_service1.nasl script by re-attempting service identification on systems where initial detection failed. The root cause is incomplete or intermittent service discovery due to network connectivity problems. An attacker could exploit this by identifying and targeting vulnerable services that were initially missed, potentially leading to compromise. There are no known CVEs associated with this specific plugin functionality itself; it’s a scanning technique rather than an exploitable flaw.

• Root cause: Intermittent network connectivity preventing initial service detection.
• Exploit mechanism: An attacker identifies running services through repeated scans and exploits any vulnerabilities present in those services. For example, if port 25 is detected as SMTP, the attacker could attempt a remote code execution exploit on an unpatched mail server.
• Scope: All network-connected systems are potentially affected.

3. Detection and Assessment

Confirming vulnerability involves checking scan logs for missed services and re-running the scan to verify detection. A quick check is reviewing recent scan results for incomplete service lists. Thorough assessment requires a full system scan with this plugin enabled.

• Quick checks: Review Nessus or similar scanner output for any instances where service detection was skipped or reported as inconclusive.
• Scanning: Use the “Service Detection (2nd Pass)” plugin ID within your vulnerability scanner (e.g., Nessus). This is an example only, and results should be interpreted carefully.
• Logs and evidence: Examine scan logs for entries indicating service detection failures or incomplete scans. Specific log file paths depend on the scanning tool used.

nessuscli scan -d  --plugin-id 64381

4. Solution / Remediation Steps

The solution involves ensuring comprehensive service detection during vulnerability scans and addressing any identified vulnerabilities. These steps focus on improving scan coverage, not a direct fix for a system flaw.

4.1 Preparation

• Backups are generally not required for this process as it’s a scanning activity. Stop no services unless specifically requested by the scanner.
• Dependencies: Ensure your vulnerability scanner is up to date and configured correctly. Roll back involves reverting to previous scan configurations if issues arise.
• Change window needs: No specific change window is required, but scheduling scans during off-peak hours is recommended. Approval may be needed depending on internal policies.

4.2 Implementation

1. Step 1: Enable the “Service Detection (2nd Pass)” plugin in your vulnerability scanner configuration.
2. Step 2: Run a full system scan against all target assets.
3. Step 3: Review the scan results for any newly detected services.
4. Step 4: Address any vulnerabilities identified in the discovered services using appropriate patching or mitigation techniques.

4.3 Config or Code Example

Before

# Plugin disabled in scan configuration
plugin_list = [12345, 67890]

After

# Plugin enabled in scan configuration
plugin_list = [12345, 67890, 64381]

4.4 Security Practices Relevant to This Vulnerability

Practices that directly address this vulnerability type include a robust patch management process and regular vulnerability scanning. Least privilege can reduce the impact of exploited services. Input validation is less relevant here, but important for the *services* detected.

• Practice 1: Regular vulnerability scanning to identify exposed services promptly.
• Practice 2: Patch cadence – maintain up-to-date software versions on all systems to address known vulnerabilities in identified services.

4.5 Automation (Optional)

# Example Ansible playbook snippet to ensure plugin is enabled in Nessus
- name: Ensure Service Detection (2nd Pass) plugin is enabled
  nessuscli:
    state: present
    plugin_id: 64381
    scan_id: "{{ scan_id }}" # Replace with your scan ID. Be careful!

5. Verification / Validation

Confirm the fix by re-running the scan and verifying that all expected services are detected. A negative test involves confirming no previously missed services remain undetected. Perform a basic service smoke test to ensure functionality is not impacted.

• Re-test: Re-run the “Service Detection (2nd Pass)” plugin and confirm it no longer reports any skipped or inconclusive service detections.
• Monitoring: Monitor scan logs for new service detections that were previously missed (example only).

nessuscli scan -d  --plugin-id 64381 | grep "Service detected"

6. Preventive Measures and Monitoring

Preventive measures include updating security baselines to include regular vulnerability scanning with comprehensive service detection. CI/CD pipelines can incorporate SAST or SCA tools to identify vulnerable services early in the development lifecycle, for example. A sensible patch review cycle is also important.

• Baselines: Update your security baseline to mandate weekly or monthly vulnerability scans including this plugin.
• Asset and patch process: Implement a regular patch review cycle, ideally within 72 hours of vendor advisories being released.

7. Risks, Side Effects, and Roll Back

Risks include increased scan duration due to the additional service detection pass. Service impacts are unlikely but possible if the scanner triggers false positives or interferes with network traffic. Roll back involves disabling the plugin in your scan configuration.

• Risk or side effect 1: Increased scan time due to more thorough service discovery. Mitigation: Schedule scans during off-peak hours.
• Roll back:
  1. Step 1: Disable the “Service Detection (2nd Pass)” plugin in your vulnerability scanner configuration.
  2. Step 2: Re-run scans to verify previous functionality is restored.

8. References and Resources

• Vendor advisory or bulletin: Tenable Nessus Plugin Details – Service Detection (2nd Pass)
• NVD or CVE entry: Not applicable, as this is a scanning technique not an exploitable flaw.
• Product or platform documentation relevant to the fix