Company lists · Data refreshed September 2026

Top 25 Cybersecurity defense companies based in the United Kingdom

There are 1,147 cybersecurity defense companies headquartered in the United Kingdom (RevenueBase, September 2026). RevenueBase 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, how directly it supports the match, and when it was last checked. Data refreshed September 1, 2026.

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. Evidence rates how directly each company's own description names cybersecurity defense companies: strong (names it), partial (names part of it), indirect (matched on its full profile rather than the summary shown). Click a count to unlock that company's people.
#CompanyHeadquartersEmployeesContactsVerified emails
1
SophosStrong evidence

“Sophos is a cybersecurity leader defending organizations globally with an AI-driven platform and expert-led services.”

Source: company website · checked Sep 1, 2026
Abingdon, United Kingdom5,001-10,0004,9632,711
2
DarktracePartial 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: company website · checked Sep 1, 2026
Cambridge, United Kingdom1,001-5,0002,5901,791
3
ZerofoxIndirect evidence

“ZeroFox is the solution to discover, validate, and disrupt external cyber threats before they harm revenue or reputation.”

Source: company website · checked Sep 1, 2026
United Kingdom501-1,000894382
4
SISAPartial 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: company website · checked Sep 1, 2026
Leicester, United Kingdom201-500739253
5
ROKEPartial 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: company website · checked Sep 1, 2026
Manchester, United Kingdom1,001-5,000684410
6
EverfoxIndirect evidence

“Everfox delivers trusted connectivity to protect the world's most critical environments, safeguarding the sensitive information behind decision advantage.”

Source: company website · checked Sep 1, 2026
London, United Kingdom1,001-5,00063513
7
MASSIndirect evidence

“MASS, part of the Cohort plc group, helps you realise the value of your data.”

Source: company website · checked Sep 1, 2026
Lincoln, United Kingdom201-500633203
8
WithsecurePartial evidence

“WithSecure™ is Europe's cybersecurity partner of choice.”

Source: company website · checked Sep 1, 2026
London, United Kingdom501-1,000614329
9
BridewellIndirect 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: company website · checked Sep 1, 2026
Edinburgh, United Kingdom201-500304189
10
Quorum CyberIndirect evidence

“At Quorum Cyber, we're on a mission to help good people win.”

Source: company website · checked Sep 1, 2026
Edinburgh, United Kingdom201-500292177
11
The Redesign GroupPartial evidence

“The Redesign Group is a global technology and cybersecurity consulting firm leveraging design thinking, interdependent subject matter expertise, and emerging technology solutions…”

Source: company website · checked Sep 1, 2026
London, United Kingdom201-500201140
12

“Ensuring your business is handling cyber security risks effectively has never been more important.”

Source: company website · checked Sep 1, 2026
London, United Kingdom51-20016962
13
Exclusive Networks UKPartial 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: company website · checked Sep 1, 2026
Mansfield, United Kingdom201-500168118
14
CyberfortIndirect 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: company website · checked Sep 1, 2026
Thatcham, United Kingdom51-20016088
15
Cybersec ConsultingIndirect evidence

“CyberSec Consulting, headquartered in the UAE and serving the iMETA market, is a distinguished professional Cyber Security and Consulting services company.”

Source: company website · checked Sep 1, 2026
London, United Kingdom201-50014176
16
CCL Solutions GroupIndirect 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: company website · checked Sep 1, 2026
Stratford Upon Avon, United Kingdom51-20013668
17
Cipher سايڤرPartial evidence

“At Cipher, we're redefining digital security as the premier cybersecurity leader in the Middle East.”

Source: company website · checked Sep 1, 2026
London, United Kingdom201-50013550
18
Bulletproof Cyber SecurityIndirect evidence

“Bulletproof is now part of WorkNest Secure.”

Source: company website · checked Sep 1, 2026
London, United Kingdom51-20011875
19
Foresite CybersecurityIndirect evidence

“As the world becomes more connected, our lives and businesses are more vulnerable.”

Source: company website · checked Sep 1, 2026
Farnborough, United Kingdom51-20010067
20

“As an independent IT security specialist, Caretower provide comprehensive solutions to individual problems, thus allowing our recommendations to be unbiased.”

Source: company website · checked Sep 1, 2026
London, United Kingdom201-5009712
21
CyberoneIndirect 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: company website · checked Sep 1, 2026
London, United Kingdom51-2009639
22
Wavenet CyberguardIndirect evidence

“CyberGuard Technologies is the security division of Wavenet.”

Source: company website · checked Sep 1, 2026
London, United Kingdom201-5008658
23
CybersmartPartial evidence

Cybersecurity should be simple.”

Source: company website · checked Sep 1, 2026
London, United Kingdom51-2008355
24
Reliance CyberIndirect evidence

“At Reliance Cyber, we believe in truly partnering with our customers.”

Source: company website · checked Sep 1, 2026
Waterloo, United Kingdom51-2008047
25

“For over 20 years, TDI’s one and only passion has been delivering cybersecurity solutions to effectively manage the business of cyber.”

Source: company website · checked Sep 1, 2026
Windsor, United Kingdom51-2007139

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
1-10Median size (employees)
LondonLargest hub · 487 HQs
2,970Contacts with mobile numbers
Sep 1, 2026Data refreshed

Companies by employee count

1-10
669
11-50
331
51-200
100
201-500
24
501-1,000
8
1,001-5,000
6
5,001-10,000
2

Cybersecurity defense companies by metro

MetroCompanies
Cybersecurity defense companies in London487
Cybersecurity defense companies in Manchester42
Cybersecurity defense companies in Cheltenham23
Cybersecurity defense companies in Birmingham22
Cybersecurity defense companies in Cambridge14
Cybersecurity defense companies in Bristol13
Cybersecurity defense companies in Edinburgh12

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 evidence rating on every row are there so you can check each match yourself.

Source
The RevenueBase company graph: 21.3 million companies and 398.9 million professional contacts resolved from primary sources.
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.
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 an evidence rating so you can judge each match yourself.
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.

Frequently asked

How many cybersecurity defense companies are there based in the United Kingdom?

There are 1,147 cybersecurity defense companies headquartered in the United Kingdom as of September 2026 (RevenueBase).

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 contact data platform. Its company graph covers 21.3 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, the same data that powers RevenueBase's B2B data products and the free research portal.