External Network Penetration Testing

External network penetration testing typically costs between £3,500 and £10,000 depending on the number of external IP addresses, complexity of your perimeter, and scope of testing. A standard external test for 1-20 IP addresses averages £6,000 for 3-5 days of testing. Larger organisations with 50+ IP addresses and complex cloud infrastructure typically cost £8,000-£10,000. We provide fixed-price quotes after reviewing your IP ranges and infrastructure architecture.

External penetration testing simulates an attacker on the open internet attempting to breach your organisation. It targets your public-facing assets (firewalls, VPN gateways, mail servers, web applications, and cloud management interfaces) to find exploitable weaknesses before real attackers do. Unlike automated vulnerability scanning, external penetration testing involves manual exploitation, attack chain construction, and OSINT-led discovery to demonstrate real-world business impact.

External penetration testing simulates an attacker with no prior access to your network, testing only what is publicly visible from the internet: your firewalls, VPN gateways, web applications, and cloud management interfaces. Internal penetration testing simulates an attacker who has already gained a foothold inside your network, testing lateral movement, Active Directory security, and privilege escalation. Most organisations that require comprehensive assurance conduct both. A CREST-accredited provider will scope the correct combination based on your compliance requirements and threat model.

External penetration testing covers all internet-facing assets within the agreed scope: firewall and router interfaces, VPN gateways (including SSL VPN), web applications and APIs, mail servers (SMTP, OWA, Exchange Online), DNS infrastructure (including zone transfer testing), remote access portals, cloud management consoles and exposed storage (AWS S3, Azure Blob), and any other services accessible from the public internet. Scope is defined during the pre-engagement scoping call and documented in the test authorisation letter.

We recommend annual testing at minimum, or after any material infrastructure change: cloud migrations, new VPN endpoints, firewall rule changes, or new application deployments. PCI DSS 11.3 mandates annual external penetration testing (and after significant changes). ISO 27001:2022 Annex A 8.8 requires a managed programme of technical vulnerability testing. Cyber Essentials Plus requires an external vulnerability assessment as part of recertification.

No. A vulnerability scan is an automated check for known patches. A penetration test is a manual, human-led simulation that attempts to actually exploit those vulnerabilities, chain them together, and find logic flaws that scanners miss. Vulnerability scanners might identify 100 potential issues, but a penetration test confirms which ones are actually exploitable and demonstrates real-world attack paths that matter to your business.

Our external network penetration testers hold industry-recognised certifications including CREST CRT (CREST Registered Tester), CREST CCT (Certified), and Offensive Security OSCP. All engagements are conducted by certified testers; automated tooling is used only as a discovery accelerator, never as the primary testing mechanism. Precursor Security is a CREST Member Company. Our accreditation can be verified at crest-approved.org.

External testing is designed to be non-disruptive and safe for production environments. We coordinate testing windows with your team and avoid destructive attacks like volumetric DDoS. However, in rare cases, exploitation attempts may trigger security alerts or cause temporary service degradation (similar to real attacker activity). We maintain abort codes and immediately cease testing if any critical systems are at risk.

Generally, no. We test for vulnerabilities that could lead to DoS (like weak application logic), but we do not perform volumetric DDoS attacks as they can disrupt your actual business operations.