Company lists · Data verified August 2026

Top 25 Defense cybersecurity companies based in the United Kingdom

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

Compiled by the RevenueBase Data Team Verified Aug 28, 2026 638 companies tracked

There are 638 defense cybersecurity companies headquartered in the United Kingdom (RevenueBase, August 2026). RevenueBase tracks 16,231 professional contacts across them, including 6,467 with verified work emails and 2,060 with mobile numbers. London is the largest hub.

This list covers defense cybersecurity 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. Data current as of August 28, 2026.

638Companies

16,231Contacts tracked

6,467Verified emails

2,060Mobile numbers

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The 25 largest defense cybersecurity companies based in the United Kingdom

Ranked by team size

Top 25 of 638 defense cybersecurity companies based in the United Kingdom, ranked by team size, largest first. Data verified Aug 28, 2026. Click a count to unlock that company's people.
#	Company	HQ	Employees	Contacts	Verified emails
1	Sophos	Abingdon	5,001-10,000	4,963	2,711
2	SISA	Leicester	201-500	739	253
3	ROKE	Manchester	1,001-5,000	684	410
4	Enea AB	Belfast	501-1,000	638	208
5	Everfox	London	1,001-5,000	635	13
6	MASS	Lincoln	201-500	633	203
7	Bridewell	Edinburgh	201-500	304	189
8	Quorum Cyber	Edinburgh	201-500	292	177
9	The Redesign Group	London	201-500	201	140
10	Sixworks An IBM Company	Farnborough	51-200	185	132
11	Exclusive Networks UK	Mansfield	201-500	168	118
12	Sapphire	Newcastle Upon Tyne	51-200	165	59
13	Cyberfort	Thatcham	51-200	160	88
14	Cybersec Consulting	London	201-500	141	76
15	Cipher سايڤر	London	201-500	135	50
16	Khipu Networks	Fleet	51-200	129	94
17	Foresite Cybersecurity	Farnborough	51-200	100	67
18	ITC Secure	London	51-200	87	39
19	Wavenet Cyberguard	London	201-500	86	58
20	Cybersmart	London	51-200	83	55
21	Reliance Cyber	Waterloo	51-200	80	47
22	Synoptix	Bristol	51-200	76	11
23	TDI Tetrad Digital Integrity	Windsor	51-200	71	39
24	Eset UK	Bournemouth	51-200	66	41
25	Covertswarm	London	51-200	65	41

Showing 25 of 638 defense cybersecurity companies based in the United Kingdom

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Defense cybersecurity companies based in the United Kingdom at a glance

As of Aug 28, 2026

1-10Median size (employees)

LondonLargest hub · 265 HQs

2,060Contacts with mobile numbers

10Emails re-verified in last 30 days

Companies by employee count

1-10

345

11-50

197

51-200

201-500

501-1,000

1,001-5,000

5,001-10,000

Defense cybersecurity companies by metro

Metro	Companies
Defense cybersecurity companies in London	265
Defense cybersecurity companies in Manchester	23
Defense cybersecurity companies in Cheltenham	13
Defense cybersecurity companies in Birmingham	11
Defense cybersecurity companies in Cambridge	9
Defense cybersecurity companies in Edinburgh	7
Defense cybersecurity companies in Bristol	7

How this list was built

Source: The RevenueBase company graph: 21.3 million companies and 398.9 million professional contacts resolved from primary sources.
Inclusion: Companies whose own business descriptions match “defense cybersecurity companies”, with match quality audited by blind human judging, and headquartered in the United Kingdom.
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: Contact records re-verify on a rolling cadence; 10 contacts on this list were re-verified in the last 30 days.
Refresh: Lists are refreshed periodically as the underlying company graph is re-verified. Last verified Aug 28, 2026.

Frequently asked

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

There are 638 defense cybersecurity companies headquartered in the United Kingdom as of August 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 defense cybersecurity companies?

London leads with 265 headquartered companies, followed by Manchester (23) and Cheltenham (13).

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 6,467 verified decision-maker contacts tracked across these 638 companies.

How current is this list?

The list is refreshed periodically as the underlying company graph is re-verified. It was last verified on August 28, 2026.

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Related lists

Defense cybersecurity companies by geography

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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.