Company lists · Data verified August 2026

Top 25 Computer security companies based in the United Kingdom

Name: Computer security 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 310 companies tracked

There are 310 computer security companies headquartered in the United Kingdom (RevenueBase, August 2026). RevenueBase tracks 8,567 professional contacts across them, including 4,089 with verified work emails and 1,109 with mobile numbers. London is the largest hub.

This list covers computer security 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.

310Companies

8,567Contacts tracked

4,089Verified emails

1,109Mobile numbers

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The 25 largest computer security companies based in the United Kingdom

Ranked by team size

Top 25 of 310 computer security 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	Quorum Cyber	Edinburgh	201-500	292	177
4	Cyberfort	Thatcham	51-200	160	88
5	Cipher سايڤر	London	201-500	135	50
6	Khipu Networks	Fleet	51-200	129	94
7	Bulletproof Cyber Security	London	51-200	118	75
8	Foresite Cybersecurity	Farnborough	51-200	100	67
9	Titania LTD	London	51-200	89	47
10	Becrypt	London	51-200	69	56
11	Eset UK	Bournemouth	51-200	66	41
12	Garrison NOW A Part Of Everfox	London	51-200	59	2
13	Adarma Security	Edinburgh	201-500	52	23
14	Coretech Security	Cheltenham	51-200	41	7
15	Omerta	Saffron Walden	51-200	38	15
16	Syxsense, An Absolute Security Company	Basingstoke	51-200	37	23
17	defense.com	Stevenage	51-200	32	13
18	Acumen Cyber	Glasgow	11-50	31	23
19	Precursor Security	Leeds	11-50	31	17
20	Cyber Security Specialists	Altrincham Manchester	11-50	27	9
21	Encode	London	51-200	25	9
22	AMR Cybersecurity	Cheltenham	11-50	23	17
23	Clearswift	Berkshire	201-500	19	4
24	Infosec K2k	London	51-200	17	8
25	CST Limited Computer Security Technology	London	11-50	17	2

Showing 25 of 310 computer security companies based in the United Kingdom

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Computer security companies based in the United Kingdom at a glance

As of Aug 28, 2026

1-10Median size (employees)

LondonLargest hub · 119 HQs

1,109Contacts with mobile numbers

19Emails re-verified in last 30 days

Companies by employee count

1-10

173

11-50

51-200

201-500

501-1,000

5,001-10,000

10001+

Computer security companies by metro

Metro	Companies
Computer security companies in London	119
Computer security companies in Manchester	9
Computer security companies in Birmingham	5
Computer security companies in Edinburgh	5
Computer security companies in Glasgow	4
Computer security companies in Cheltenham	4
Computer security companies in Sheffield	4

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 “computer security 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; 19 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 computer security companies are there based in the United Kingdom?

There are 310 computer security 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 computer security companies?

London leads with 119 headquartered companies, followed by Manchester (9) and Birmingham (5).

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 4,089 verified decision-maker contacts tracked across these 310 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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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.