Vendor Network Security Assessment Template

Stop sending generic security questionnaires that return useless answers. Your CISO wants network topology diagrams, firewall rulesets, and proof of segmentation — not checkbox confirmations.

The Vendor Network Security Assessment Template targets the technical controls that actually matter for third-party network risk. Built from incident response data across 500+ breaches, it focuses on the network vulnerabilities attackers exploit: flat networks, overprivileged service accounts, and missing egress controls.

This DDQ template translates complex network security requirements into answerable questions. Vendors provide evidence, not promises. You get network diagrams showing segmentation, penetration test reports validating controls, and specific configuration standards they follow.

Use this template when onboarding SaaS providers with API access, managed service providers on your network, or any vendor processing sensitive data. The risk-weighted scoring automatically adjusts based on vendor criticality and data access levels.

Core Sections of the Network Security Assessment

Network Architecture and Segmentation (Questions 1-15)

Request network topology diagrams showing security zones, DMZ placement, and production/non-production separation. Critical vendors must demonstrate micro-segmentation between customer environments.

Evidence requirements:

• Current network architecture diagrams (Visio or equivalent)
• VLAN configuration documentation
• Network segmentation test results
• Zero Trust implementation roadmap (if applicable)

Control mapping: SOC 2 CC6.1, ISO 27001 A.13.1, PCI DSS 1.1

Access Control and Authentication (Questions 16-25)

Evaluate network access controls including VPN configuration, jump box usage, and privileged access management. Focus on service account permissions and API authentication methods.

Evidence requirements:

• Remote access policy and procedures
• MFA enforcement screenshots
• Service account inventory with permission levels
• Network access control (NAC) deployment status

Control mapping: ISO 27001 A.9.1, NIST SP 800-53 AC-2, CIS Control 6

Firewall and Perimeter Security (Questions 26-35)

Assess firewall rule management, change control processes, and default-deny configurations. Request evidence of regular rule reviews and decommissioning procedures.

Evidence requirements:

• Firewall ruleset summary (sanitized)
• Change management tickets for last 3 rule changes
• Annual firewall review documentation
• Web Application Firewall (WAF) configuration

Control mapping: PCI DSS 1.1.6, ISO 27001 A.13.1.1, CSA CCM IVS-06

Monitoring and Incident Response (Questions 36-45)

Verify network monitoring capabilities, SIEM integration, and incident response procedures. Emphasize detection of lateral movement and data exfiltration.

Evidence requirements:

• Network monitoring dashboard screenshots
• Sample incident response runbook
• Mean time to detect/respond metrics
• DDoS mitigation capabilities

Control mapping: SOC 2 CC7.3, ISO 27001 A.12.4, NIST CSF DE.AE

Vulnerability Management (Questions 46-50+)

Document vulnerability scanning frequency, patch management processes, and penetration testing schedules. Require evidence of remediation timelines based on severity.

Evidence requirements:

• Recent vulnerability scan reports (executive summary)
• Penetration test findings and remediation proof
• Patch management policy with SLAs
• Bug bounty program details (if applicable)

Control mapping: ISO 27001 A.12.6, PCI DSS 11.2, CIS Control 7

Industry-Specific Applications

Financial Services

Add questions on:

• Network isolation for payment processing
• SWIFT CSP compliance evidence
• Trading system latency requirements
• Regulatory reporting network controls

Compliance frameworks: PCI DSS, FFIEC CAT, SWIFT CSP

Healthcare

Add questions on:

• PHI transmission encryption methods
• Medical device network segmentation
• HIPAA-compliant logging retention
• Telehealth platform security

Compliance frameworks: HIPAA Technical Safeguards, HITRUST CSF

Technology/SaaS

Add questions on:

• Multi-tenant isolation mechanisms
• API rate limiting and DDoS protection
• Content Delivery Network (CDN) security
• DevOps pipeline network controls

Compliance frameworks: SOC 2, CSA STAR, ISO 27017

Implementation Best Practices

1. Pre-Assessment Scoping Call

Schedule 30-minute technical calls before sending the DDQ. Explain evidence requirements and provide examples of acceptable documentation. This reduces back-and-forth by 70%.

2. Risk-Based Question Sets

Create three versions:

• Critical vendors (50+ questions): Full assessment including architecture reviews
• Medium-risk vendors (25 questions): Focus on perimeter security and access controls
• Low-risk vendors (10 questions): Basic firewall and patching confirmation

3. Evidence Validation Checklist

Create acceptance criteria for each evidence type:

• Network diagrams must show security zones and data flows
• Pentest reports must be less than 12 months old
• Firewall rules must demonstrate least-privilege principles

4. Automated Scoring Logic

Implement weighted scoring:

• Critical controls (MFA, segmentation): 3x weight
• Standard controls (monitoring, patching): 1x weight
• Compensating controls accepted with justification

Common Implementation Mistakes

1. Accepting Generic Policy Documents

Policies prove intent, not implementation. Demand technical evidence: screenshots, configurations, test results. If they claim "defense in depth," ask for the network diagram showing each layer.

2. Ignoring Cloud-Native Architecture

Traditional network assessments miss cloud-specific risks. Add questions on VPC configuration, security group rules, and cloud-native firewall services (AWS Security Groups, Azure NSGs).

3. One-Size-Fits-All Scoring

A flat network might be acceptable for a marketing vendor but critical failure for a payment processor. Adjust scoring thresholds based on data sensitivity and access levels.

4. Skipping Re-Assessment Triggers

Define clear triggers for re-assessment:

• Architecture changes (new data center, cloud migration)
• Security incidents at vendor
• Regulatory changes affecting network requirements
• M&A activity changing vendor infrastructure

5. Missing Continuous Monitoring

Annual assessments miss deteriorating controls. Require quarterly vulnerability scan summaries and immediate notification of material network changes.

Frequently Asked Questions

How do I handle vendors who claim network diagrams are confidential?

Offer to sign a specific NDA for technical documentation. Alternatively, accept sanitized diagrams that show zones and flows without IP addresses. If they refuse both options, increase their risk score accordingly.

What evidence should I require for cloud-only vendors without traditional network infrastructure?

Focus on cloud network controls: VPC flow logs, security group configurations, cloud WAF rules, and API gateway settings. Request terraform/CloudFormation templates or Azure Policy assignments as evidence.

How many questions should I include for different vendor tiers?

Critical vendors: 50-75 questions. High-risk: 35-50 questions. Medium-risk: 20-35 questions. Low-risk: 10-20 questions. Adjust based on data sensitivity and integration depth.

What's the best way to validate firewall rules without seeing sensitive IP addresses?

Request a rules matrix showing source zone, destination zone, ports/protocols, and business justification. Alternatively, ask for screenshots with IPs redacted but showing rule structure and deny rules.

How often should I reassess vendor network security?

Critical vendors: annually with quarterly check-ins. High-risk: annually. Medium-risk: every 18 months. Low-risk: every 2 years. Trigger immediate reassessment after incidents or architecture changes.

Should I require penetration test reports from all vendors?

Require annual pentest reports from critical and high-risk vendors. Accept vulnerability scans from medium-risk vendors. Low-risk vendors can provide attestation of security testing.

How do I assess network security for vendors in different regulatory jurisdictions?

Create regional variants addressing specific requirements: GDPR data localization, China cybersecurity law network controls, or Russia data protection requirements. Core security controls remain consistent.