CREST-Certified External Penetration Testing for UK Businesses
External network penetration testing and external infrastructure penetration testing aligned to PTES, NIST SP 800-115, the OWASP Testing Guide, and OSSTMM / SANS methodologies. Manual exploitation of exposed services, weak SSL/TLS, leaked credentials, subdomain takeover, and patch-level RCE. Fixed-price quotes within 24 hours.
Your attack surface is bigger than you think.
Modern UK businesses run a sprawling attack surface — and effective attack surface management requires more than passive scanning. Public IP ranges, forgotten subdomains, third-party hosting, leaked credentials on paste sites, exposed admin panels with default credentials, dev / staging environments left routable. External attackers don’t ask for an asset list — they enumerate it.
Our external infrastructure penetration testing combines OSINT (Shodan, Censys, theHarvester, dark-web credential scanning) with manual exploitation against every reachable service. Reports satisfy ISO 27001 Annex A.13.1, PCI DSS Req 11.3, NCSC vulnerability management guidance, and Cyber Essentials boundary firewalls — without translation work.
12 ATTACK CATEGORIES
What We Test in External Penetration Testing
Aligned to PTES, NIST SP 800-115, and the OWASP Testing Guide. Each category exploited manually with industry-standard tooling — Nmap, Burp Suite Pro, custom scripts, and OSINT platforms.
Exposed Services & Open Ports
Discovery and verification of every reachable port, banner-grabbing service identification, and version fingerprinting against the public IP range.
Outdated Software / Unpatched CVEs
Manual exploitation of unpatched services. Validated proof-of-concept rather than scanner false positives.
Weak SSL/TLS Configuration
Cipher suite analysis, certificate validation, downgrade attacks, expired certs, weak DH parameters, deprecated protocol versions.
Credential Leakage & Defaults
Dark-web credential scans, paste-site hits, default-credential testing on every reachable management interface.
Subdomain Takeover
Dangling DNS records pointing to deprovisioned cloud resources. Identification + safe proof-of-takeover via test record.
Email Security (SPF/DKIM/DMARC)
Domain spoofing exposure, SPF/DKIM/DMARC validation, BIMI / MTA-STS posture, anti-phishing posture review.
VPN / RDP / SSH Exposure
Brute-force resilience, MFA enforcement, version exploits (e.g. CVE-2019-19781 Citrix), credential stuffing tolerance.
Cloud Edge Misconfiguration
Exposed S3 / Blob containers, leaked CloudFront origins, misconfigured WAFs, SaaS edge endpoints with weak auth.
Web Admin Panels Exposed
phpMyAdmin, Jenkins, Kibana, GitLab, Grafana, Prometheus — discovered through hostname enumeration and brute-forced for default / weak credentials.
Information Disclosure
Verbose error messages, exposed git repositories, .DS_Store, server-status, /metrics endpoints, robots.txt secrets.
Forgotten Dev / Staging
Discovery of dev.*, staging.*, test.*, qa.*, uat.* subdomains routable from the public internet — typically with weaker controls than production.
Bypass of WAF / DDoS Edge
Origin IP exposure via SSL certificate logs, historical DNS, mail-server identification — bypass of CloudFlare / AWS Shield / Akamai protection.
FOUR-PHASE METHODOLOGY
External Penetration Testing — From OSINT to Attestation
Discovery before exploitation. External network penetration testing starts where attackers start — open-source recon. We never test what we don’t know. We never miss what’s reachable.
OSINT & Recon
Active Discovery
Manual Exploitation
Report & Retest
Verified Accreditations Auditors Accept
Every accreditation independently issued by a recognised UK certification body. Click CREST to verify our membership.
COMPLIANCE READY
External Reports Mapped to Every Framework
Findings tagged to specific control IDs in your compliance framework. Audit teams submit directly without translation.
ISO 27001 (Annex A)
A.13.1 network security, A.13.2 information transfer, A.12.6.1 vulnerability management evidence.
PCI DSS
Req 11.3.1 / 11.3.2 external network testing — required for all PCI-scoped environments processing payment data.
Cyber Essentials Plus
Boundary firewall and external testing scope. Aligned with IASME audit-grade evidence requirements.
NCSC Vulnerability Management
External-facing assets validated against NCSC vulnerability management guidance — public-sector aligned.
SOC 2 Type I & II
CC7.1 vulnerability identification and CC6.6 logical access controls evidence for SOC 2 audits.
NHS DSPT & UK GDPR Art 32
External attack-surface evidence for NHS supply-chain partners and any regulated processor of UK personal data.
TRANSPARENT PRICING
Transparent External Penetration Testing Pricing
All tiers include the same depth of testing. Price varies by attack-surface complexity — number of public IPs, subdomain count, cloud edge breadth, and exposed services.
Depends on attack-surface size
1-20 public IPs, single subnet, ≤10 subdomains. Standard external posture review. Typically 2-3 day engagement.
- ✓Free retests included
- ✓Free rescheduling
- ✓No cancellation fees
- ✓24-hour scope to active testing
- ✓Live findings to client portal
- ✓Executive + technical report
- ✓60-min walkthrough call
- ✓Letter of attestation
Depends on attack-surface size
20-100 IPs, multi-subnet, cloud edge, ≤50 subdomains, mixed VPN / RDP / SaaS exposure. Typically 5-7 day engagement.
- ✓Free retests included
- ✓Free rescheduling
- ✓No cancellation fees
- ✓24-hour scope to active testing
- ✓Live findings to client portal
- ✓Executive + technical report
- ✓60-min walkthrough call
- ✓Letter of attestation
Depends on attack-surface size
100+ IPs, hybrid cloud, multi-region, 50+ subdomains, regulated workloads, Cyber Essentials Plus scope. Typically 8-12 day engagement.
- ✓Free retests included
- ✓Free rescheduling
- ✓No cancellation fees
- ✓24-hour scope to active testing
- ✓Live findings to client portal
- ✓Executive + technical report
- ✓60-min walkthrough call
- ✓Letter of attestation
External Penetration Testing for Your Sector
External attack-surface risk varies by sector. We test the controls your regulators and auditors specifically require.
Fintech
Open Banking edge, FCA SYSC exposure, payment-platform DNS, Cloudflare-protected origin scrutiny, PCI scoping.
SaaS
Multi-tenant cloud edge, SSO endpoints, customer subdomain takeover, exposed admin / metrics endpoints, SOC 2 evidence.
Healthcare
NHS supply-chain perimeter, telehealth edge, EHR integrations, DSP Toolkit external evidence.
Insurance
Claims-portal exposure, broker-VPN scrutiny, cyber-underwriter evidence, FCA / PRA Operational Resilience.
Law
Privileged-data perimeter, partner-portal exposure, document-management edge, SRA Cyber Standard alignment.
Public Sector
Citizen-facing edge, GOV.UK integrations, NCSC-aligned, SC-cleared testers available, CCS / G-Cloud evidence.
What You Actually Get
Five things that distinguish our external testing from automated scans and box-tick competitors.
What You Get From External Penetration Testing
Discovery-First Methodology
No Scanner-Only Reports
Boundary Firewall + Cyber Essentials Aligned
UK CREST + IASME + ISO 27001 + ISO 9001
Frequently Asked
How long does an external penetration test take?
A small external engagement (1-20 IPs, ≤10 subdomains) typically takes 2-3 working days. Mid-market (20-100 IPs, cloud edge) takes 5-7 days. Enterprise (100+ IPs, multi-region, hybrid cloud) takes 8-12 days. Test duration is determined during scoping based on attack-surface size.
How much does external infrastructure penetration testing cost in the UK?
Small engagements range £4,000-£6,500. Mid-market (most commonly commissioned) £6,500-£14,000. Enterprise £14,000+. All quotes are fixed-price after scoping. Day rate equivalent is £1,000-£1,500 per CREST-certified tester per day.
What methodology do you follow?
We follow PTES (Penetration Testing Execution Standard), NIST SP 800-115, and the OWASP Testing Guide. Each engagement starts with passive OSINT before any active testing. We test exactly what’s reachable from the public internet — what an external attacker would actually see. Combined with internal network penetration testing, you get full attack-path coverage.
Do you use Shodan, Censys, and OSINT tools?
Yes. Shodan, Censys, FOFA, theHarvester, and certificate transparency log mining are core to our recon phase. We also perform dark-web credential exposure checks for your domain and key personnel. OSINT is included in every external engagement at no additional cost.
Do you check for subdomain takeover?
Yes — every external engagement checks for dangling DNS records pointing to deprovisioned cloud resources. Subdomain takeover is a common high-impact finding (e.g., GitHub Pages / Heroku / S3 / Azure CDN). We provide safe proof-of-takeover evidence without claiming the resource.
Can you test our cloud edge (AWS / Azure / GCP)?
Yes — external testing covers cloud edge surface: load balancers, public S3 / Blob containers, exposed CloudFront origins, lambda function URLs, VPC peering misconfiguration. For full configuration review of cloud control planes we recommend our dedicated AWS, Azure, or GCP cloud security review.
What’s the difference between external and internal pen testing?
External network penetration testing simulates an attacker with no access — they only see your public-facing services. Internal testing simulates an attacker who’s already on your network (compromised laptop, malicious insider, post-phish foothold). They’re complementary; CREST and NCSC recommend both annually for high-assurance organisations.
Do you provide evidence for Cyber Essentials Plus?
Yes — external pen testing maps directly to Cyber Essentials Plus boundary firewall and external scanning scope. We provide the test report, attestation letter, and remediation evidence in the format IASME assessors require. We are an IASME Cyber Essentials Certifying Body ourselves.
Will testing impact production?
External network penetration testing is largely passive at first (banner-grabbing, version detection, OSINT). Active exploitation phases use safe-by-default checks. Any potentially disruptive test (exploit attempts on rare services) is paused for explicit client approval before execution. We do not run DoS attacks against production.
Do you test from the UK or internationally?
Testing originates from controlled test infrastructure in the UK or EU by default. We can rotate source addresses for scenarios where an attacker would use specific geo origins (Russia, China, etc.) — but only when this matches your real threat model and has been explicitly authorised.
Are your testers UK-based and what certifications do they hold?
All external infrastructure testers are vetted UK or international engineers. Relevant certifications across the team include CREST CRT and CCT INF (infrastructure), OSCP, OSCE, and protocol-specific specialisms. SC-cleared testers are available for public-sector and regulated-financial engagements.
Do you sign NDAs?
Yes. Standard NDA before any technical detail is shared, and we operate under a project-specific master agreement that includes data handling, deliverable IP, and breach notification clauses. Custom MSAs and AUP terms are accepted for enterprise and public-sector clients.
Book an External Pen Test Scoping Call
30 minutes with a CREST-certified infrastructure tester. Fixed-price quote within 24 hours. No sales pipeline.







