Company lists · Data refreshed September 2026
Top 24 Network security testing firms based in London, United Kingdom
RevenueBase identified 266 network security testing firms headquartered in London, United Kingdom as of September 2026 and tracks 2,755 professional contacts across them, including 466 with verified work emails. Across the United Kingdom, London is the largest hub for this category.
This list covers network security testing firms headquartered in London, United Kingdom, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 29, 2026.
Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.
The 24 largest network security testing firms based in London, United Kingdom
Ranked by team size| # | Company | Contacts | |||
|---|---|---|---|---|---|
| 1 | 87 contacts → | ||||
Partial evidence “ITC Secure is an advisory-led cyber security services company.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 2 | 77 contacts → | ||||
Partial evidence “White Hat, part of the EPAM group, is an award-winning cyber intelligence and offensive security company that leverages an attacker’s perspective to shape innovative, proactive…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 3 | 64 contacts → | ||||
Indirect evidence “YOU DESERVE TO BE HACKED®.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 4 | 57 contacts → | ||||
Partial evidence “We deliver services in Cybersecurity, Application Security and DevOps and are trusted by some of the world’s leading brands to maximise the value of their security investments and…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 5 | 52 contacts → | ||||
Indirect evidence “At Hexegic we are not just passionate about protecting data through our Cyber services we are passionate about helping companies release the potential of the data they hold…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 6 | 51 contacts → | ||||
Strong evidence “Redscan is an award-winning provider of managed security services, specialising in Managed Detection and Response, Penetration Testing and Red Teaming.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 7 | 44 contacts → | ||||
Partial evidence “Our Red Team security consultants are elite technical experts with worldwide Red Team service experience, and a respected reputation of delivering red team services for SME’s.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 8 | 33 contacts → | ||||
Partial evidence “NotSoSecure Training, part of Claranet Cyber Security.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 9 | 32 contacts → | ||||
Partial evidence “CYB3R Group, is a leading provider of comprehensive Cyber Security, IT and Communications Solutions.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 10 | 25 contacts → | ||||
Partial evidence “Encode is now part of Obrela Security Industries collectively delivering cutting edge Cyber Security Services, empowering organizations to better protect against cyber threats.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 11 | 24 contacts → | ||||
Partial evidence “SSL247 (A Sectigo Company) has nearly 20 years of security consulting experience operating in 18 different markets globally.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 12 | 23 contacts → | ||||
Indirect evidence “Toro was founded on creating the UK's first Red Team penetration test - and then attacking hundreds of clients by hacking their systems, influencing / social engineering staff and…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 13 | 21 contacts → | ||||
Partial evidence “Templar Executives is an award winning, international Cyber Security advisory services and solutions company operating at the highest levels across the public and private sectors.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 14 | 20 contacts → | ||||
Partial evidence “Secure Purple is a leading cyber security and digital safety firm that provides innovative solutions and services to help organisations and individuals stay protected in the…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 15 | 18 contacts → | ||||
Partial evidence “th4ts3cur1ty.company supplies cyber security services internationally.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 16 | 17 contacts → | ||||
Indirect evidence “We are a leading cybersecurity services organization with more than a decade of proven expertise in consulting, solution implementation and managed services.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 17 | 17 contacts → | ||||
Partial evidence “We are a London based specialist supplier of cyber defence solution and information security services.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 18 | 15 contacts → | ||||
Indirect evidence “Who We Are DataSixth delivers Cybersecurity Intelligence.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 19 | 15 contacts → | ||||
Partial evidence “Founded in 2006, Tranchulas is a multinational cyber security company having its offices in London, San Francisco, Budapest and Islamabad.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 20 | 15 contacts → | ||||
Partial evidence “is an ISO 9001:2015 and ISO/IEC 27001:2022 certified, DPIIT-recognized cybersecurity company delivering structured External Vulnerability Assessment & Penetration Testing (VAPT)…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 21 | 13 contacts → | ||||
Partial evidence “Delivering Excellence in Cyber Security At ZDL, we believe that effective risk management requires a holistic 360° approach.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 22 | 13 contacts → | ||||
Indirect evidence “In today’s world, cyber threats are complex and multilayered, so complete protection is not achievable through a single solution or product, that's why GoAllSecure provides a 360°…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 23 | 13 contacts → | ||||
Indirect evidence “Our mission at SOCGuardians is to empower organizations to operate confidently in a digital world by providing cutting-edge cybersecurity services.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 24 | 12 contacts → | ||||
Partial evidence “At Cyber Armed Security, we protect organisations worldwide from evolving cyber threats through intelligence-driven ethical hacking.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
RevenueBase Smart Search
RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: network security testing firms. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.
- Strong evidence
- The company's own public description of its business names network security testing firms.
- Partial evidence
- Its own public description names part of network security testing firms, so it works in or next to the category without describing itself that way.
- Indirect evidence
- The description shown does not name network security testing firms. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.
RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.
Showing 24 of 266 network security testing firms based in London, United Kingdom
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Network security testing firms based in London, United Kingdom at a glance
As of Sep 29, 2026Companies by employee count
Email recency for this list is measured across the whole United Kingdom list rather than for London, so it is reported there. Company counts and contact totals on this page are exact for London, over 266 companies.
How this list was built
Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among network security testing firms, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.
- Source
- The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
- What qualifies
- Companies headquartered in London, United Kingdom whose own description of what they do matches “network security testing firms”. Matching reads each company's description, not its industry code or its name.
- RevenueBase Smart Search
- RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names network security testing firms), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
- What we exclude
- Companies whose own description does not clearly place them among network security testing firms, and records with no verified work email. Companies headquartered outside London are excluded even when they keep an office there.
- Match quality
- In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
- Ranking
- Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
- Verification
- Every listed company carries at least one verified work email, 466 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
- Refresh
- This page's figures were pulled from the company graph on September 29, 2026. Lists refresh periodically as the graph is re-checked.
- Corrections
- Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.
Network security testing firms by metro in the United Kingdom
Frequently asked
What is RevenueBase Smart Search?
RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names network security testing firms, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.
How many network security testing firms are there based in London, United Kingdom?
RevenueBase identified 266 network security testing firms headquartered in London, United Kingdom as of September 2026, matched on each company's own description of what it does rather than its industry code.
What is the largest company on this list?
ITC Secure, headquartered in London, tops this list with the largest team on record.
Which city in the United Kingdom has the most network security testing firms?
London leads the United Kingdom with 266 headquartered companies, followed by Manchester (34) and Birmingham (16).
How do I get contact information for these companies?
A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 466 verified decision-maker contacts tracked across these 266 companies.
How current is this list?
The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 29, 2026.
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About this data
RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.
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