Company lists · Data refreshed September 2026

Top 25 Cybersecurity defense companies based in the United Kingdom

Name: Cybersecurity defense companies based in the United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 1, 2026 1,147 companies tracked

RevenueBase identified 1,147 cybersecurity defense companies headquartered in the United Kingdom as of September 2026 and tracks 23,499 professional contacts across them, including 10,280 with verified work emails and 2,970 with mobile numbers. London is the largest hub.

This list covers cybersecurity defense companies headquartered in the 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 1, 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.

How to read this list RevenueBase Smart Search rating on every row Refreshed Sep 1, 2026 86% judged on-target in blind review

1,147Companies

23,499Contacts tracked

10,280Verified emails

2,970Mobile numbers

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The 25 largest cybersecurity defense companies based in the United Kingdom

Ranked by team size

Top 25 of 1,147 cybersecurity defense companies based in the United Kingdom, ranked by team size, largest first. Data refreshed Sep 1, 2026. RevenueBase Smart Search rates how each company's information relates to cybersecurity defense companies: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#	Company	RevenueBase Smart Search	Headquarters	Employees	Contacts
1	Sophos	Strong evidence	Abingdon, United Kingdom	5,001-10,000	4,963 contacts →
	Strong evidence “Sophos is a cybersecurity leader defending organizations globally with an AI-driven platform and expert-led services.” Source: RevenueBase Database · checked Sep 1, 2026
2	Darktrace	Partial evidence	Cambridge, United Kingdom	1,001-5,000	2,590 contacts →
	Partial evidence “Darktrace is a global leader in AI cybersecurity, providing the essential cybersecurity platform to secure organizations today and for an ever-changing future.” Source: RevenueBase Database · checked Sep 1, 2026
3	Zerofox	Indirect evidence	United Kingdom	501-1,000	894 contacts →
	Indirect evidence “ZeroFox is the solution to discover, validate, and disrupt external cyber threats before they harm revenue or reputation.” Source: RevenueBase Database · checked Sep 1, 2026
4	SISA	Partial evidence	Leicester, United Kingdom	201-500	739 contacts →
	Partial evidence “SISA is a global forensics-driven cybersecurity solutions company, trusted by leading organizations for securing their businesses with robust preventive, detective, and corrective…” Source: RevenueBase Database · checked Sep 1, 2026
5	ROKE	Partial evidence	Manchester, United Kingdom	1,001-5,000	684 contacts →
	Partial evidence “At Roke, we stand at the forefront of defence and security, delivering cutting-edge intelligence and engineering solutions that protect nations, troops, borders, and businesses.” Source: RevenueBase Database · checked Sep 1, 2026
6	Everfox	Indirect evidence	London, United Kingdom	1,001-5,000	635 contacts →
	Indirect evidence “Everfox delivers trusted connectivity to protect the world's most critical environments, safeguarding the sensitive information behind decision advantage.” Source: RevenueBase Database · checked Sep 1, 2026
7	MASS	Indirect evidence	Lincoln, United Kingdom	201-500	633 contacts →
	Indirect evidence “MASS, part of the Cohort plc group, helps you realise the value of your data.” Source: RevenueBase Database · checked Sep 1, 2026
8	Withsecure	Partial evidence	London, United Kingdom	501-1,000	614 contacts →
	Partial evidence “WithSecure™ is Europe's cybersecurity partner of choice.” Source: RevenueBase Database · checked Sep 1, 2026
9	Bridewell	Indirect evidence	Edinburgh, United Kingdom	201-500	304 contacts →
	Indirect evidence “Bridewell is the trusted cyber security partner for organisations operating within Critical National Infrastructure (CNI), as well as companies who want the highest standard of…” Source: RevenueBase Database · checked Sep 1, 2026
10	Quorum Cyber	Indirect evidence	Edinburgh, United Kingdom	201-500	292 contacts →
	Indirect evidence “At Quorum Cyber, we're on a mission to help good people win.” Source: RevenueBase Database · checked Sep 1, 2026
11	The Redesign Group	Partial evidence	London, United Kingdom	201-500	201 contacts →
	Partial evidence “The Redesign Group is a global technology and cybersecurity consulting firm leveraging design thinking, interdependent subject matter expertise, and emerging technology solutions…” Source: RevenueBase Database · checked Sep 1, 2026
12	Risk Associates - Emea & Asia	Indirect evidence	London, United Kingdom	51-200	169 contacts →
	Indirect evidence “Ensuring your business is handling cyber security risks effectively has never been more important.” Source: RevenueBase Database · checked Sep 1, 2026
13	Exclusive Networks UK	Partial evidence	Mansfield, United Kingdom	201-500	168 contacts →
	Partial evidence “Exclusive Networks is a global trusted cybersecurity specialist for digital infrastructure helping to drive the transition to a totally trusted digital future for all people and…” Source: RevenueBase Database · checked Sep 1, 2026
14	Cyberfort	Indirect evidence	Thatcham, United Kingdom	51-200	160 contacts →
	Indirect evidence “At Cyberfort we are passionate about the cyber security services we deliver for our customers which keeps their people, data, systems and technology infrastructure secure…” Source: RevenueBase Database · checked Sep 1, 2026
15	Cybersec Consulting	Indirect evidence	London, United Kingdom	201-500	141 contacts →
	Indirect evidence “CyberSec Consulting, headquartered in the UAE and serving the iMETA market, is a distinguished professional Cyber Security and Consulting services company.” Source: RevenueBase Database · checked Sep 1, 2026
16	CCL Solutions Group	Indirect evidence	Stratford Upon Avon, United Kingdom	51-200	136 contacts →
	Indirect evidence “CCL Solutions Group is one of Europe’s leading digital forensics, digital investigation and cyber security specialists, supporting law enforcement, government agencies, military…” Source: RevenueBase Database · checked Sep 1, 2026
17	Cipher سايڤر	Partial evidence	London, United Kingdom	201-500	135 contacts →
	Partial evidence “At Cipher, we're redefining digital security as the premier cybersecurity leader in the Middle East.” Source: RevenueBase Database · checked Sep 1, 2026
18	Bulletproof Cyber Security	Indirect evidence	London, United Kingdom	51-200	118 contacts →
	Indirect evidence “Bulletproof is now part of WorkNest Secure.” Source: RevenueBase Database · checked Sep 1, 2026
19	Foresite Cybersecurity	Indirect evidence	Farnborough, United Kingdom	51-200	100 contacts →
	Indirect evidence “As the world becomes more connected, our lives and businesses are more vulnerable.” Source: RevenueBase Database · checked Sep 1, 2026
20	Caretower An Integrity360 Company	Indirect evidence	London, United Kingdom	201-500	97 contacts →
	Indirect evidence “As an independent IT security specialist, Caretower provide comprehensive solutions to individual problems, thus allowing our recommendations to be unbiased.” Source: RevenueBase Database · checked Sep 1, 2026
21	Cyberone	Indirect evidence	London, United Kingdom	51-200	96 contacts →
	Indirect evidence “CyberOne is a Microsoft Security Elite Partner and one of only 100 global Microsoft partners recognised with Microsoft-Verified Managed XDR solution status.” Source: RevenueBase Database · checked Sep 1, 2026
22	Wavenet Cyberguard	Indirect evidence	London, United Kingdom	201-500	86 contacts →
	Indirect evidence “CyberGuard Technologies is the security division of Wavenet.” Source: RevenueBase Database · checked Sep 1, 2026
23	Cybersmart	Partial evidence	London, United Kingdom	51-200	83 contacts →
	Partial evidence “Cybersecurity should be simple.” Source: RevenueBase Database · checked Sep 1, 2026
24	Reliance Cyber	Indirect evidence	Waterloo, United Kingdom	51-200	80 contacts →
	Indirect evidence “At Reliance Cyber, we believe in truly partnering with our customers.” Source: RevenueBase Database · checked Sep 1, 2026
25	TDI Tetrad Digital Integrity	Partial evidence	Windsor, United Kingdom	51-200	71 contacts →
	Partial evidence “For over 20 years, TDI’s one and only passion has been delivering cybersecurity solutions to effectively manage the business of cyber.” Source: RevenueBase Database · checked Sep 1, 2026

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: cybersecurity defense companies. 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 cybersecurity defense companies.
Partial evidence: Its own public description names part of cybersecurity defense companies, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name cybersecurity defense companies. 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 25 of 1,147 cybersecurity defense companies based in the United Kingdom

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Cybersecurity defense companies based in the United Kingdom at a glance

As of Sep 1, 2026

43.7%Verified-email coverage

12.6%Mobile-number coverage

20.5Average contacts per company

1-10Median size (employees)

42.5%Largest-city concentration · London

Sep 1, 2026Page data refreshed

Companies by employee count

1-10

669

11-50

331

51-200

100

201-500

501-1,000

1,001-5,000

5,001-10,000

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 cybersecurity defense companies, 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 the United Kingdom whose own description of what they do matches “cybersecurity defense companies”. 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 cybersecurity defense companies), 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 cybersecurity defense companies, and records with no verified work email. Companies headquartered outside United Kingdom 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, 10,280 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 1, 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.

Cybersecurity defense companies by metro

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 cybersecurity defense companies, 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 cybersecurity defense companies are there based in the United Kingdom?

RevenueBase identified 1,147 cybersecurity defense companies headquartered in the 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?

Sophos, headquartered in Abingdon, tops this list with the largest team on record.

Which city has the most cybersecurity defense companies?

London leads with 487 headquartered companies, followed by Manchester (42) and Cheltenham (23).

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 10,280 verified decision-maker contacts tracked across these 1,147 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 1, 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.