VoIP and SIP Penetration Testing
Toll fraud is quiet, immediate and expensive. A PBX reachable from the internet with weak extension credentials can place international calls all weekend, and the first anyone knows is the bill. CREST-certified testers, fixed price from £2,990, scoped in 24 hours.
- Unlimited retesting
- No rescheduling or cancellation fees
- Fixed quote within 24 hours
“I would highly recommend EJN Labs to any organisation seeking reliable, detailed, and well-managed penetration testing services, particularly for government or enterprise-level projects.”
Imran SaghirProject Lead, SquareOne“There wasn’t another company we could find that could deliver what we needed in the timeframe we needed. The client loved it, and we got instant ROI from the engagement.”
Dan WilcocksonCo-Founder, CelloriTelephony sits with facilities or IT operations rather than security, it was installed by a supplier, and it has worked ever since. That combination means the PBX is frequently the least reviewed internet-facing system a business runs.
Why telephony gets forgotten
Two outcomes follow. The first is toll fraud: weak or guessable extension credentials and permissive dial plans let an outsider place premium-rate and international calls, which is a direct financial loss rather than an abstract risk.
The second is interception. Where signalling and media are unencrypted on the internal network, calls can be captured and replayed, which matters a great deal for legal, healthcare and financial conversations. Examples of the platforms we pen test include 3CX, Asterisk, FreePBX, Cisco and Mitel, among others.
ISO 27001, SOC 2, PCI DSS and Cyber Essentials Plus audits accept manual penetration test evidence. Scan-only evidence is generally insufficient.
SIP, PROVISIONING + INTERCEPTION
What we actually pen test on a VoIP deployment
Manual pen testing across SIP enumeration and registration, toll fraud paths, call interception, provisioning server exposure and PBX configuration.
SIP enumeration and registration
Extension and user enumeration through registration and options responses, credential strength against the extensions discovered, registration hijacking, and whether an unregistered endpoint can place calls.
Toll fraud and dial plan abuse
Dial plan analysis for international and premium-rate reachability, whether call restrictions apply to every route, trunk authentication, and out-of-hours call limits and alerting.
Call interception and media
Whether signalling and media are encrypted, capture and reconstruction of calls on the internal network, voicemail access controls, and call recording storage and retrieval.
Provisioning server exposure
Auto-provisioning endpoints, whether configuration files containing credentials are retrievable by MAC address or serial guess, TFTP and HTTP provisioning security, and firmware update integrity.
PBX management and configuration
Management interface exposure and authentication, default and shared accounts, software version against known vulnerabilities, and API and integration access.
Network position and segmentation
Whether the voice network is segmented from data, what a compromised handset reaches, VLAN hopping from a phone port, and whether the PBX can reach systems it need not.
METHODOLOGY
VoIP and SIP Penetration Testing: From Scope to Attestation
CREST-aligned methodology built on OWASP Web Security Testing Guide, OWASP ASVS, NIST SP 800-115, and PTES. Each finding maps to all four standards plus your specific compliance regime.
Reconnaissance
Application mapping, technology fingerprinting, content discovery, parameter enumeration, authentication-flow analysis, role-matrix construction.
Vulnerability Assessment
Authenticated and unauthenticated automated scanning across every user role, plus targeted manual checks for known weakness patterns.
Manual Exploitation
Hands-on testing by a CREST-certified pentester. Business-logic exploitation, chained vulnerabilities, privilege escalation, impact validation.
Reporting + Retest
Executive summary, technical report with CVSS scores and reproduction steps, walkthrough call, free retest after remediation, attestation letter.
CREDENTIALS
Verified Accreditations Auditors Accept
Every credential below is independently verifiable. UK procurement teams, FCA supervisors, ISO 27001 / SOC 2 auditors, and cyber insurance underwriters all recognise these standards.
GET YOUR QUOTE
Get a CREST VoIP pen test quote in 24 hours
A fixed-price quote back in one business day, from a named CREST assessor. No sales pipeline, no chasing.
- CREST and IASME accredited. Testing your auditors and clients already recognise.
- Fast-track testing within 24 hours where required. Free retest of every fix included.
- Live findings via your client portal, not a four-week PDF.
- Fixed price from £3,500 for a single-role, single-app scope, agreed up front. Most engagements run £5,000 and up. No day-rate surprises.
Dan WilcocksonCo-Founder, CelloriUnder NDA Further named references available on a scoping call.
- We reply within one business day with a fixed-price quote from a named CREST assessor.
- You approve the scope and we book a start date, usually within 24 hours.
- Live findings land in your client portal as we test, with a free retest of every fix.
Get your fixed pen test quote in 24 hours
Quote request received
We will reply within one business day with your fixed-price quote from a named CREST assessor.
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COMPLIANCE READY
Reports Mapped to Every Framework
Findings are explicitly tagged to the relevant control reference. Your audit team submits the report directly without translation work.
ISO 27001:2022
Annex A.8.8 management of technical vulnerabilities plus A.5.15-5.18 and A.8.2-8.5 access control validation.
SOC 2 Type I & II
CC6 logical access, CC7 system operations, CC8 change management evidence.
PCI DSS
Requirement 11.4 application penetration testing across cardholder data environments, including ecommerce penetration testing for online retail platforms.
FCA SYSC
SYSC 4.1.1R, 6.1.1R, 13 mapped to each finding for FCA-regulated firms.
UK GDPR
Article 32 effectiveness testing, customer-data security controls, ICO-acceptable evidence.
Cyber Essentials Plus
Direct certification through our IASME body status, single-vendor delivery.
PRICING
Transparent VoIP and SIP Penetration Testing Pricing
Pricing depends on app complexity, user-role count, business-logic depth, and integration surface. The day count flexes; the included deliverables stay the same across all engagements.
2 to 3 testing days
Single user role, basic CRUD application, marketing website with auth. Around 5 working days from kickoff to report.
Get a fixed quote3 to 5 testing days
Multi-role SaaS, business application with payment integration. Around 8 to 12 working days from kickoff to report.
Get a fixed quote5 to 7 testing days
Multi-tenant platform, complex authorisation matrix, integration-heavy applications. Around 15 to 20 working days from kickoff to report.
Get a fixed quotePart of Technologies We Pen Test. These are examples of the stacks we publish pages for, not a complete list. If yours is not here we still test it. Related pages:
BY SECTOR
VoIP and SIP Penetration Testing for Your Sector
Sector-specialist scoping for UK businesses with sector-specific compliance regimes and threat models.
Fintech & FCA-Regulated
FCA SYSC, Open Banking FAPI 1.0, PSD2 SCA, payment-flow scrutiny, KYC/AML testing.
Fintech sector pageSaaS Companies
SOC 2 Type I & II evidence, multi-tenant boundaries, role escalation, customer-tenant isolation.
SaaS sector pageLaw Firms
SRA Cyber Standard, privileged data, conveyancing fraud defence, partner-tier procurement.
Law firm sector pageHealthcare
NHS DTAC, DSP Toolkit v6, UK GDPR Article 32, EHR systems, telehealth platforms.
Healthcare sector pageInsurance
FCA / PRA Operational Resilience, cyber underwriting, claims data, broker portals.
Insurance sector pagePublic Sector
CCS / G-Cloud framework, NCSC-aligned, citizen-facing services, PSN-compliance scrutiny.
Public sector pageWHY EJN LABS
What You Get From VoIP and SIP Penetration Testing
Six concrete differentiators competitors don’t all match.
CREST-Certified Testers, Verifiable
Every test by a CREST-certified pen tester (CRT, CCT APP, CCT INF where applicable). Verify our company status at crest-approved.org.
24-Hour Startup, Where Required
From signed scope to active testing in a single business day for incident response, audit deadlines, or regulator-driven timelines.
Live Findings, Not 4-Week PDFs
Critical issues reported during testing through your client portal. Your team remediates while testing continues.
Audit-Ready Reports
Executive summary plus full technical report with CVSS scores and explicit framework mappings (ISO 27001, SOC 2, PCI DSS, FCA SYSC).
Free Retests, Standard
Verify remediation of every finding before close-out. Letter of attestation for audit submission included. Most competitors charge £1,500-£3,000 per retest.
UK-Based CREST Testers
Every engagement performed by vetted, UK-based CREST-certified testers, matched to your needs, security clearance, and compliance scope.
FAQ
Frequently Asked
Will you actually place calls?
Only with agreement and within limits you set. We demonstrate toll fraud reachability using test destinations and short durations, or by showing the dial plan permits it, rather than running up a real bill.
Which platforms do you cover?
3CX, Asterisk, FreePBX, Cisco, Mitel and Avaya among them, plus hosted SIP trunk configurations. These are examples rather than a complete list and the methodology applies to whatever you run.
Our phone system is hosted. What is in scope?
Your configuration, your trunk, your dial plan, your handsets and your network. We do not attack the provider’s platform, and most toll fraud findings are in the customer configuration anyway.
Will testing disrupt calls?
No. We avoid volume and denial testing against production entirely, and anything with a risk of disruption is scheduled out of hours or run against a test extension.
Does this matter for compliance?
Where calls carry personal, health or payment data it does. Findings are mapped to ISO 27001, GDPR and PCI DSS where card details are taken over the phone.
20+ CREST-accredited testing services in one place
Web, mobile, API, cloud, AI, infrastructure, red team. Pick the test that fits your environment.
Get a fixed price for your VoIP estate
Tell us the platform, whether it is hosted or on-premises, and roughly how many extensions and trunks. Fixed-price quote within one business day.
