The Best Penetration Testing Companies for UK Telecoms and Connectivity Providers (2026)

The best penetration testing companies for UK telecoms and connectivity providers in 2026 are listed below. Each one holds a CREST penetration testing accreditation and shows public evidence of work in the telecoms sector, and each is compared on published pricing, retests and report turnaround. Ofcom’s TBEST scheme is covered separately, because it needs a provider approved for it.

1. SecAlliance

SecAlliance (Security Alliance) is a UK threat intelligence and intelligence-led testing specialist with a dedicated TBEST service page, which describes TBEST as the telecommunications member of the BEST family of intelligence-led simulated attack frameworks and states its experience of the telecommunications industry and its supply chain. Its CREST listing also names TBEST among the frameworks it delivers. CREST-accredited for penetration testing, cyber threat intelligence, and threat intelligence for simulated attack. Verified: CREST Marketplace listing.

2. EJN Labs

EJN Labs is a CREST-accredited UK penetration testing consultancy with a dedicated telecoms penetration testing service covering subscriber portals, provisioning APIs, SIM management and SIM swap workflows, reseller and wholesale channel portals, internal networks and Active Directory, external infrastructure, and VoIP and SIP services. It is the only company on this list that publishes its pricing. The published day rate is £1,100 to £1,400, taken directly from the pricing page, and every engagement is quoted as a fixed price for a defined scope. The business holds ISO 27001, ISO 9001, Cyber Essentials and Cyber Essentials Plus, and is an IASME Certification Body for Cyber Essentials and Cyber Essentials Plus. Verified: CREST Marketplace listing for EJN Labs.

For a telecoms provider, what the fixed price includes matters as much as the number. Retesting of fixed findings is free until the issues are resolved, so the evidence that your fixes worked, which is what Ofcom engagement, a wholesale partner or a buyer’s due diligence asks for, is part of the original quote. Findings are delivered live to a client portal as they are confirmed, so your engineering team can start fixing on day one. The report arrives on the last day of testing, and it is the only report date stated on this list. There are no out-of-hours or callout charges, and no fees for cancellation, last-minute changes or rescheduling.

Testing is delivered by UK-based, CREST-certified penetration testers, which matters when the systems in scope hold subscriber identity and billing data. Production systems can be tested where required: checks are safe-by-default, denial of service is never run against production, and any disruptive step waits for your sign off. Out of hours or overnight slots are available so live subscriber and network operations are not interrupted. Reports give each finding a CVSS score and prioritised remediation guidance, followed by a walkthrough call, and are written to be handed to a regulator, a partner or an auditor.

Telecoms providers can use a CREST-accredited company or an approved TBEST provider, depending on what their requirement states. TBEST is Ofcom’s threat-led scheme, and a TBEST engagement needs a provider approved for it. EJN Labs is CREST-accredited, and its place is the testing around it: the portals, APIs and networks that sit beside a TBEST engagement. SecAlliance’s published TBEST service keeps it first. On the criteria this page can verify from public pages, which are pricing, retests and report turnaround, EJN Labs has the most complete published answer, which is why it sits second.

3. SECFORCE

SECFORCE is a UK offensive security consultancy whose guide to TBEST security testing describes itself as a CREST-approved provider of TBEST threat intelligence and testing services. Its web application penetration testing page states that it offers retesting to confirm closure of findings. CREST-accredited for penetration testing, vulnerability assessment and threat led penetration testing. Verified: CREST Marketplace listing.

4. NCC Group

NCC Group is a UK-headquartered global cyber security business that publishes telecoms case studies, including a 5G standalone security testing programme for a major UK mobile operator and a legacy mobile network case study covering older 2G, 3G and 4G domains. CREST-accredited for penetration testing, vulnerability assessment, incident response, security operations centre, threat led penetration testing and threat intelligence. Verified: CREST Marketplace listing.

5. Kroll (incorporating Redscan)

Kroll is a global risk advisory firm whose UK cyber practice absorbed Redscan. Its application security case study describes testing around 200 applications for a global telecommunications company over a partnership of more than four years, later extended to networking, IoT and 5G mobile devices. Kroll holds CREST accreditation for penetration testing, incident response and security operations centre. Redscan has no standalone listing, so check the Kroll entry. Verified: CREST Marketplace listing for Kroll LLC.

6. Fortbridge

Fortbridge is a UK penetration testing company that publishes a penetration testing guide for the UK Telecoms Security Act, with a section on how it can help telecoms providers. Its white box testing page states that it verifies remediation and re-tests to confirm an issue is resolved. CREST-accredited for penetration testing. Verified: CREST Marketplace listing.

7. Resillion

Resillion is a testing and assurance company with a UK headquarters on its CREST listing and a published case study on penetration testing for a European telecommunications provider, covering a new cloud analytics platform. Its penetration testing page states it is happy to retest. CREST-accredited for penetration testing, vulnerability assessment, security operations centre and threat led penetration testing. Verified: CREST Marketplace listing.

How we selected these companies

Every company on this list passed the same two entry checks: a live listing in the CREST Marketplace supplier directory confirming penetration testing accreditation, and public evidence of work in the telecoms sector. We then recorded what each company publishes about pricing, retests and report turnaround. All pages were checked on 7 October 2026.

• CREST accreditation, verified. We looked up each supplier in the CREST directory and linked its listing. No listing, no entry: brands absorbed into a parent company appear under the parent.
• Telecoms sector evidence. A general penetration testing company was not enough. Each entry needed a public page showing telecoms work: a dedicated telecoms or TBEST service page, a telecoms case study, or a guide written for telecoms providers. Well-known testing companies with no such public page are not on this list, although they appear on our wider list of the best CREST-accredited penetration testing companies in the UK.
• Published pricing. We recorded whether a company publishes its own prices on a public page. General statements about what the market charges were not counted as a company’s own pricing.
• Retests and report turnaround. A telecoms provider often has to show a regulator, a wholesale partner or a buyer that findings were fixed. Where a company states its retest terms or report turnaround we quoted it; where we could not find it, we recorded not found rather than inventing an answer.

How the companies compare

All seven companies hold verified CREST penetration testing accreditation, show a United Kingdom headquarters on their listing except Kroll, and have public telecoms sector evidence. The practical differences are in what they publish.

Accreditation is taken from each company’s CREST Marketplace listing. Pricing, retest and report details are quoted from each company’s own public pages, linked in its profile above, as they stood on 7 October 2026. Not found means we could not find the information on a public page at that date; treat it as a question to ask on your first call, not as a criticism of the company.

Do telecoms providers have to have a penetration test?

No rule names a penetration test as mandatory for a UK telecoms provider. The legal duty comes from the Telecommunications (Security) Act 2021 and the Electronic Communications (Security Measures) Regulations 2022. Regulation 14 requires a network or service provider, at appropriate intervals, to carry out or arrange tests that are appropriate and proportionate, and the tests must involve simulating, so far as is possible, techniques that might be expected to be used by a person seeking to cause a security compromise.

The government’s Telecommunications Security Code of Practice (version 1.1, 14 July 2026) is guidance on how to meet that duty, and Ofcom monitors and enforces compliance. Paragraph 13.9 of the Code says that testing, or red team exercising, is to verify the security defences of the network, and that it is essential the testing simulates, so far as possible, real-world attacks. Paragraph 13.11 calls Ofcom’s TBEST scheme a strongly recommended example of this type of testing. It is recommended, not mandated.

In practice the Code’s expectations scale with a provider’s relevant turnover, so ask your compliance lead which tier applies before scoping. Testing that is usually asked for outside TBEST is application-layer work on the systems that hold subscriber identity and provisioning authority, and evidence of retesting after fixes. For scope and cost, see our telecoms penetration testing service.

What a telecoms provider should ask a penetration testing company

1. Which legal entity holds your CREST accreditation? Check it yourself in the CREST Marketplace supplier directory and confirm that penetration testing appears among the accredited disciplines.
2. Are you approved to deliver TBEST, and if not, what will you test around it? TBEST needs a provider approved for the scheme, so ask a supplier plainly which side of that line it sits on.
3. Have you tested subscriber portals, provisioning APIs and SIM swap workflows before? These are where account takeover and provisioning abuse show up, so ask what a typical test of them covers.
4. How will you test live network and subscriber systems without disrupting them? Ask about safe testing windows, rules of engagement and how disruptive checks are handled.
5. Is a retest included, and for how long? Regulators, partners and buyers ask for evidence that findings were fixed, so a retest that is capped or charged separately changes the real price.
6. What is the fixed price for our scope, and when do we get the report? Ask for a day count and a day rate, not a range.

Get a quote

Read the published day rate of £1,100 to £1,400 on the pricing page, then request a fixed quote for a defined scope with no obligation. Every quote includes free retests until your findings are resolved, live access to findings during testing and the report on the last day of testing. Get a penetration testing quote, or read more about penetration testing for UK telecoms and connectivity providers.

Related: TSA 2021 and Penetration Testing: What Ofcom Checks When It Audits Telecoms Providers and Penetration Testing Cost for UK Telecoms Providers.