Company lists · Data refreshed September 2026

Top 23 Security testing companies based in London, United Kingdom

Name: Security testing companies based in London, United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 13, 2026 170 companies tracked

RevenueBase identified 170 security testing companies headquartered in London, United Kingdom as of September 2026 and tracks 2,262 professional contacts across them, including 365 with verified work emails and 212 with mobile numbers. London is the largest hub.

This list covers security testing companies 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 13, 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 HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 13, 2026 86% judged on-target in blind review

170Companies

2,262Contacts tracked

365Verified emails

212Mobile numbers

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The 23 largest security testing companies based in London, United Kingdom

Ranked by team size

Top 23 of 170 security testing companies based in London, United Kingdom, ranked by team size, largest first. Data refreshed Sep 13, 2026. RevenueBase Smart Search rates how each company's information relates to security testing 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	Covertswarm	Indirect evidence	London, United KingdomHQ checked Sep 13, 2026	51-200	64 contacts →
	Indirect evidence “YOU DESERVE TO BE HACKED®.” Source: RevenueBase Database · checked Sep 13, 2026
2	Intruder	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	51-200	61 contacts →
	Partial evidence “Intruder's continuous exposure management platform helps security, IT, and engineering teams stop breaches before they start.” Source: RevenueBase Database · checked Sep 13, 2026
3	Riversafe	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
4	Redscan, A Kroll Business	Strong evidence	London, United KingdomHQ checked Sep 13, 2026	51-200	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 13, 2026
5	Redhunt Labs	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	36 contacts →
	Partial evidence “RedHunt Labs is a research-driven cybersecurity company delivering Continuous Threat Exposure Management (CTEM), PTaaS, and AI Exposure Security.” Source: RevenueBase Database · checked Sep 13, 2026
6	Notsosecure Training Part Of Claranet Cyber Security	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	1,001-5,000	33 contacts →
	Partial evidence “NotSoSecure Training, part of Claranet Cyber Security.” Source: RevenueBase Database · checked Sep 13, 2026
7	Ssl247 A Sectigo Company	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	51-200	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 13, 2026
8	Toro Solutions	Indirect evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
9	Secure Purple	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
10	th4ts3cur1ty.company	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	18 contacts →
	Partial evidence “th4ts3cur1ty.company supplies cyber security services internationally.” Source: RevenueBase Database · checked Sep 13, 2026
11	Sinevis	Indirect evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
12	CST Limited Computer Security Technology	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	17 contacts →
	Partial evidence “We are a London based specialist supplier of cyber defence solution and information security services.” Source: RevenueBase Database · checked Sep 13, 2026
13	Datasixth Consulting	Indirect evidence	London, United KingdomHQ checked Sep 13, 2026	51-200	15 contacts →
	Indirect evidence “Who We Are DataSixth delivers Cybersecurity Intelligence.” Source: RevenueBase Database · checked Sep 13, 2026
14	Eh1-Infotech Cybersecurity	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
15	Socguardians LTD	Indirect evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
16	Cyber Armed Security	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	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 13, 2026
17	CYTAL	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	11 contacts →
	Partial evidence “CyTAL exists to help developers, manufacturers and their customers to improve the security and resilience of products and systems.” Source: RevenueBase Database · checked Sep 13, 2026
18	Disclosure Cybersecurity	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	11 contacts →
	Partial evidence “Disclosure Cybersecurity Ltd is a specialist cyber security company, formed by professionals with extensive experience and wide exposure in the cyber security market.” Source: RevenueBase Database · checked Sep 13, 2026
19	Secureteam LTD	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	10 contacts →
	Partial evidence “SecureTeam are a UK-based information security practice, specialising in all areas of cybersecurity.” Source: RevenueBase Database · checked Sep 13, 2026
20	Pentiq	Strong evidence	London, United KingdomHQ checked Sep 13, 2026	1-10	10 contacts →
	Strong evidence “We are a UK-based Cyber Security company offering a comprehensive portfolio specialising in innovative solutions for Penetration Testing, Training, Compliance, Consulting, and…” Source: RevenueBase Database · checked Sep 13, 2026
21	Validato	Indirect evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	10 contacts →
	Indirect evidence “Validato helps organisations continuously validate and strengthen their cybersecurity controls using safe-to-use, production-ready Breach and Attack Simulation (BAS).” Source: RevenueBase Database · checked Sep 13, 2026
22	Icyberdefence	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	8 contacts →
	Partial evidence “iCyberDefence is a boutique cybersecurity services firm that offers a wide range of security consulting and security engineering services with the necessary products and tools.” Source: RevenueBase Database · checked Sep 13, 2026
23	Xray Cybersecurity	Partial evidence	London, United KingdomHQ checked Sep 13, 2026	11-50	8 contacts →
	Partial evidence “We provide a wide range of Penetration Testing Services: External & Internal Network Pentest, Application Pentest and Social Engineering Attacks.” Source: RevenueBase Database · checked Sep 13, 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: security testing 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 security testing companies.
Partial evidence: Its own public description names part of security testing companies, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name security testing 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 23 of 170 security testing companies based in London, United Kingdom

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Security testing companies based in London, United Kingdom at a glance

As of Sep 13, 2026

16.1%Verified-email coverage

9.4%Mobile-number coverage

13.3Average contacts per company

1-10Median size (employees)

104.1%Largest-city concentration · London

Sep 13, 2026Page data refreshed

Companies by employee count

1-10

11-50

51-200

201-500

501-1,000

1,001-5,000

Freshness & accuracy

How recently the business emails were verified and the company information checked

Email last verified

Median 16.0d

2870–30

7331–60

161–90

090–180

4180+

Company record updated

Median 77.0d

00–30

61831–60

1,23761–90

30590–180

102180+

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 security testing 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 London, United Kingdom whose own description of what they do matches “security testing 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 security testing 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 security testing companies, 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, 365 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 13, 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.

Security testing companies by metro in the United Kingdom

Security testing companies in London177
Security testing companies in Manchester26

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 security testing 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 security testing companies are there based in London, United Kingdom?

RevenueBase identified 170 security testing companies 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?

Covertswarm, headquartered in London, tops this list with the largest team on record.

Which city has the most security testing companies?

London leads with 177 headquartered companies, followed by Manchester (26) and Birmingham (14).

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 365 verified decision-maker contacts tracked across these 170 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 13, 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.