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Seed Cybersecurity companies in London

Companies defending or attacking software, networks, and cloud infrastructure. Filtered to Seed-stage companies headquartered in London.

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Built from a search like: “Top Seed Cybersecurity companies in London”

Ranked by current headcount across Seed Cybersecurity companies in London. Refreshed daily.

  1. 1
    Intruder· London, England, United Kingdom

    Intruder was founded in 2015 to help solve the information overload crisis in vulnerability management. Having worked both as an ethical hacker for tier one companies, and for blue teams defending critical national infrastructure, Founder Chris Wallis noticed that while vulnerability management tools were great at finding issues, they were less useful when it came to prioritizing them, tracking them, and timely alerting when problems arose. Quite simply - the most important issues were often getting lost in the noise.Intruder's mission from day one has been to help divide the needles from the haystack, focusing on what matters, while ignoring the rest. Effective cyber security is about getting the basics right. Intruder helps you do that, saving time on the easy stuff, so you can focus on the rest.Since its inception in 2015, Intruder has been awarded multiple accolades, was selected for GCHQ's Cyber Accelerator, and was included on Deloitte's Tech Fast 50 2023 list as the fastest-growing cybersecurity company in the UK. It is now proud to have over 3,000 happy customers all over the world.============================We're hiring! https://careers.intruder.io============================Intruder's mission from day one has been to help divide the needles from the haystack, focusing on what matters, while ignoring the rest. Effective cyber security is about getting the basics right. Intruder helps you do that, saving time on the easy stuff, so you can focus on the rest.Since its inception in 2015, Intruder has been awarded multiple accolades, was selected for GCHQ's Cyber Accelerator, and was included on Deloitte's Tech Fast 50 2023 list as the fastest-growing cybersecurity company in the UK. It is now proud to have over 3,000 happy customers all over the world.============================We're hiring! https://careers.intruder.io============================

    • Seed
    • 84 employees
    • Founded 2015
  2. 2
    SecureFlag· London, England, United Kingdom

    SecureFlag helps organizations prevent vulnerabilities at scale by embedding security into every stage of software development, from architecture decisions to the moment code is written.From secure design to secure code, we transform how enterprises manage application risk.AI coding assistants have rapidly changed the risk equation. Developers are shipping faster than ever—and shipping more vulnerabilities with them, at a pace traditional AppSec tools can't match.As a Developer Security Enablement Platform, SecureFlag brings hands-on secure coding training and automated threat modeling into one place:-ThreatCanvas generates complete threat models in seconds, making risks visible at the design stage—before AI-generated (or human-written) code ever hits the repo.-SecureFlag Training upskills developers in live development environments, teaching them to recognize and fix the exact vulnerabilities AI tools are most likely to introduce.-Compliance reporting delivers continuous, audit-ready evidence across standards such as ISO, SOC 2, PCI, HIPAA, and ASVS.What enterprise teams see:➔ 21% fewer new security tickets➔ 27% faster vulnerability remediation➔ 24% less time spent on security rework➔ 2.4x ROI within 12 monthsTrusted by 300+ organizations in 30+ countries to turn secure-by-design from a principle into a measurable security control.Book a demo to see SecureFlag in action.

    • Seed
    • 67 employees
    • Founded 2019
  3. 3
    Goldilock Secure· London, England, United Kingdom

    In today’s hyper-connected digital world, protecting any organization's assets against novel, sophisticated and aggressive cyber threats means reversing that hyper-connection when needed...powerfully, completely and outside the view of adversaries. Cutting them off while maintaining control of systems is essential. Our FireBreakTM️ Physical Connection Controller is a new breed of device that is controlled remotely, invisibly to the network, and allows you to disconnect either entire networks or selected segments at the physical level. We enforce total physical isolation-based segmentation. Any network, whether large enterprise, service provider, critical infrastructure or defense sector, needs to protect services, data, and business operations. Using FireBreakTM️ physical connection controller “uniquely achieves what no other solution can.” says Gregory Akers, Advanced Security Research, CISCO. Goldilock delivers advanced cyber defense solutions for network and infrastructure protection at the physical layer. FireBreakTM️ is a powerful physical connection controller that remotely, and invisibly, allows the disconnection of either whole networks or selected segments.

    • Seed
    • 46 employees
    • Founded 2020
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  5. 4
    SURF SECURITY· London, England, United Kingdom

    The business landscape is fundamentally changing – the way and location of work has been transformed. Furthermore, with mass migration to the cloud, SaaS is vital. All this creates new risks - numerous points of access from multiple devices and multiple locations increase the attack surface. To address these attacks, your security solution should fundamentally change as well. That's where SURF enters.SURF provides users with freedom of work, letting them interact with applications, data, and each other securely. It addresses the critical business asset neglected by security experts for years: The browser.The browser is the access frontier for everything: users, data, corporate assets, applications, development activities - and cyber criminals, too.SURF Security has transformed the browser into your strongest security asset while providing complete end-user privacy – all with full compliance. Through this centralized platform, SURF insists on identity-first access to all SaaS and corporate assets to guarantee a secured and frictionless user experience. SURF enhances security, performance, and productivity for end-users and applications – faster than ever before.

    • Seed
    • 33 employees
    • Founded 2021
  6. 5
    Redflags.· London, England, United Kingdom

    A UK company developing products that reinvent the delivery of end-user security education and awareness training.

    • Seed
    • 29 employees
    • Founded 2016
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Find engineers at Seed Cybersecurity companies in London

Searching for “engineers at top Seed Cybersecurity companies in London” surfaces this slice of the market. The list above ranks Cybersecurity companies headquartered in London whose latest disclosed round is Seed, by current headcount, drawn from public LinkedIn and Crunchbase records. With 18 matching companies in Refolk’s index, this is a tight read on where the Cybersecurity talent in London is heating up.

Three filters at once narrows the field hard. The companies that survive all three - Seed, Cybersecurity, in London - are usually the most targeted recruiting pool a hiring manager can ask for. Senior engineers, founding designers, and product leads here are about to become Cybersecurity’s next operators and angel investors.

Refolk converts this list into a live search. Ask for “senior engineers at Seed Cybersecurity companies in London hiring” or “founders of Seed Cybersecurity companies in London who left in the last year” and Refolk returns a ranked shortlist with the evidence behind each match.

How this list is built

Refolk pulled Cybersecurity companies headquartered in London whose latest disclosed funding round is Seed from public LinkedIn and Crunchbase records, ranked them by current employee count, and kept those with at least 3 employees. The list refreshes once a day.

Last refreshed: Wed, 05 Aug 2026 11:54:58 GMT

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