Top Cybersecurity Companies in UK 2025 (Reviewed)

• The UK cybersecurity sector is rapidly expanding, generating £13.2 billion in 2024.
• Top firms include NCC Group, Pen Test Partners, Nettitude (LRQA), and others delivering penetration testing, red teaming, incident response, and managed detection.
• These providers hold major accreditations such as CREST, ISO 27001, and sector-specific certifications, serving finance, government, defence, and critical infrastructure.
• With cyber incidents risingthe NCSC handled 429 incidents in 2024choosing a trusted UK security partner is more important than ever.
• This guide profiles the leading firms and our own DeepStrike to help organizations select the right cybersecurity provider based on expertise, accreditation, and sector needs.

Cybersecurity is now a national priority in the UK. In 2024, half of UK businesses reported a cyber breach, with phishing responsible for 84% of attacks. The threats are rising: the NCSC handled 429 incidents last year, over double the previous year. In parallel, the UK security industry is growing fast sector revenue hit £13.2 billion in 2024. This makes it vital to know the top cybersecurity companies in the UK, the firms you can trust to defend your business. Below we break down the leading UK security providers, what they offer, and what sets each apart.

Why UK Cybersecurity Firms Matter in 2025

As organizations digitize, cyber risks multiply. The UK government reports that more businesses are raising security controls and investing in expertise. For example, almost two thirds of large firms now use security monitoring tools. At the same time, high impact breaches are expensive. IBM finds the average UK breach now costs £3.58 million. In short, having a skilled cybersecurity partner isn’t optional anymore; it’s essential. Top UK firms bring deep experience, often decades, cutting edge techniques, and certifications like CREST/ISO that help you stay ahead of threats.

Below we profile the leading UK cybersecurity companies, focusing on their specialties, strengths, and who they serve. Whether you need regular penetration tests, a 24/7 SOC, or a boutique red team engagement, there’s a firm tailored to your needs.

Leading UK Cybersecurity Companies

DeepStrike London, UK

DeepStrike is a next generation penetration testing firm that blends elite manual expertise with a cloud based PTaaS platform. Founded by security experts some co authored the Web Application Hacker’s Handbook, DeepStrike emphasizes hands-on testing: every engagement includes custom exploits and attack chains. They target startups and growing tech firms needing quick, ongoing assurance. Notably, DeepStrike offers rapid onboarding tests often start within 48 hours and free retesting of remediated issues for 12 months. Their team holds top certifications OSCP, OSWE, CISSP, etc. and supports compliance ISO 27001, SOC 2, PCI DSS. In essence, DeepStrike’s unique blend of creative manual pentesting and a live dashboard with Slack/Jira integration sets it apart from traditional consultancies.

NCC Group Manchester, UK

NCC Group is a global cyber consultancy listed on the FTSE 250. With over 30 years of history and 2,200 employees, NCC offers full spectrum security: penetration testing network, cloud, web, mobile, OT, red/purple teaming, threat intelligence, incident response, and managed services SOC/MDR. It pioneered “threat led” penetration testing using real attack data. NCC’s strength is scale and pedigree trusted by major banks, governments, and defense contractors. Their consultants hold advanced CREST and CHECK credentials, and they even operate UKAS accredited ISO 17025 labs for high assurance testing. In short, NCC Group is an enterprise class provider for large, regulated organizations, though their premium pricing reflects multi week, high touch engagements.

Pen Test Partners Manchester, UK

Pen Test Partners PTP is a highly technical boutique pentesting firm 100+ staff focused purely on hands-on testing since 2010. Fully CRESTand CHECK accredited plus CBEST/TIBER finance sector testing, PCI QSA, ISO 27001, PTP specializes in web/mobile/API assessments, code reviews, wireless & IoT tests, and advanced red team ops. Clients are typically critical infrastructure or finance organizations that demand maximum assurance. PTP’s consultants are often security researchers and white hat hackers, known for uncovering novel attack paths. The firm’s approach is 100% manual and innovative, eschewing scripted scans. In practice, PTP is prized for deep technical expertise and creativity. If you need a penetration test for a power grid or airport, PTP is often cited for thoroughness and ingenuity in finding hidden flaws.

Nettitude LRQA London, UK

Nettitude, now part of Lloyd’s Register/LRQA is a large UK cyber services firm that blends technical testing with compliance expertise. It offers full spectrum pentesting cloud, network, web/mobile, IoT/OT and red teaming, often bundling the results with ISO 27001, PCI DSS or other audit services. Nettitude also provides 24×7 MDR and security architecture reviews. Clients include banks, government, maritime, and energy firms where formal compliance matters. Nettitude’s “dual focus” is key: they deliver deep technical findings and executive quality, audit friendly reporting. The team is CRESTand NCSC CHECK approved, aligned with LRQA’s ISO pedigree. In short, Nettitude is a go to for regulated sectors needing both vulnerability discovery and concrete compliance documentation.

Bulletproof London, UK

Bulletproof is a UK headquartered firm 100+ staff whose sweet spot is SMBs and mid market companies needing fast, affordable compliance testing. They offer pentests for web, mobile, network, cloud and social engineering, plus red team simulations. Bulletproof’s core focus is meeting standards PCI DSS, ISO 27001, GDPR, SOC 2, HIPAA, etc. with CREST accredited testers. They provide clients an online portal to track prioritized findings and remediation. ISO 27001 certified, with OSCP level testers, Bulletproof is known for speed and service: engagements often start in days and reports are delivered in under a week. In essence, Bulletproof combines CREST standard technical testing with a friendly, rapid turnaround model ideal for growing businesses.

Secarma Manchester, UK

Secarma is a niche UK offensive security specialist est. 2001. They do infrastructure, web/mobile pentests and complex red team ops that blend cyber, physical and social techniques. Notably, Secarma has strong R&D e.g. crafting custom implants like “EndView” and offers a PTaaS style continuous testing service for long term clients. Fully CREST/CHECK accredited, their staff OSCP, GIAC, etc. have a deep persistence mindset: “we don't quit until every door is checked.” Typical clients are government agencies, healthcare NHS, fintech and energy essentially organizations facing skilled adversaries. Secarma’s strength is attacker focused creativity: they simulate nation state style threats and are known for relentless exploit chaining on multi month engagements.

Redscan Kroll Responder London, UK

Redscan, now part of Kroll, started as an independent MSSP and is best known for its 24×7 Managed Detection & Response MDR and Incident Response services, the Kroll Responder platform. It also performs pentests and red teaming as project work. Redscan’s model combines automated threat hunting tech with expert analysts. It has won industry awards e.g. “Best MSSP” at SC Awards Europe 2022 for its Kroll Responder MDR service. Major clients span finance, healthcare, and government. In sum, Redscan is a hybrid provider: its core strength is ongoing SOC/MDR backed by Kroll’s IR brand, with penetration tests as a complementary service.

Bridewell Cyber Security London, UK

Bridewell is a specialist MSP/MSSP focusing on UK critical infrastructure transport, utilities, defense. It bills itself as an end to end partner, offering everything from security consulting and DevSecOps to 24×7 SOC/MDR, threat intel, and incident response. They also do GDPR/compliance advisory and penetration testing. As Microsoft’s leading UK security partner for critical infrastructure, Bridewell leverages Azure and M365 technology e.g. secure Copilot, Azure Sentinel. Over 200 essential service organisations, airports, power, water, etc. trust Bridewell. The firm’s strengths: deep industry expertise, broad compliance services, and strong accreditations ISO 27001, Cyber Essentials, etc.. Bridewell is ideal if you’re in aviation, energy or utilities and need a managed service that aligns closely with UK tech stacks.

BAE Systems Applied Intelligence Farnborough, UK

BAE Systems Applied Intelligence is the cyber arm of defence giant BAE Systems. It offers enterprise grade solutions: penetration testing, secure cloud engineering, threat intel and large scale managed security, plus IR. BAE’s approach is “intelligence grade” they leverage big data analytics, military grade R&D, and decades of defense expertise. Serving governments, financial institutions and other critical orgs, BAE has deep ties to UK national security e.g. CPNI incident response scheme. They hold CREST/CHECK accreditations and have former Mandiant teams on staff. BAE’s strengths are its vast resources and advanced methods: think enterprise class red teams and bespoke cyber solutions. Price and delivery are enterprise level they’re not focused on SMEs.

Comparison of Top UK Cybersecurity Firms

How to Choose the Right UK Cybersecurity Partner

Selecting a cybersecurity firm depends on your needs. Follow these steps:

1. Identify Your Needs: Are you looking for a one off audit or continuous protection? If compliance is key PCI, ISO, SOC2, choose a firm with audit experience. If you need constant monitoring, look for MDR/SOC services.
2. Check Expertise: Examine each company’s specialties. For example, Pen Test Partners and DeepStrike excel at technical pentests, while Bridewell and Redscan shine in managed SOC services. Use their case studies or published reviews to gauge depth of experience.
3. Verify Accreditations: Look for CREST or NCSC CHECK accreditation for pen testing and red teaming. ISO 27001 or PCI certifications indicate maturity. Awards and client lists can also hint at credibility.
4. Industry Fit: Pick a company familiar with your sector. If you’re in finance or healthcare, partners like NCC or Secarma used to testing regulated targets may suit you. For critical national infrastructure energy, transport, Bridewell or Pen Test Partners have relevant track records.
5. Service Model: Consider delivery style. Some firms like DeepStrike or Secarma integrate testing into DevOps pipelines PTaaS, enabling faster feedback. Others like NCC or Bulletproof may use traditional report based approaches. Choose what matches your workflow.
6. Budget & Scale: Large consultancies often come at a premium multi week engagements, while boutique firms can be more cost effective for SMBs. Get quotes and compare scope to find good value.

When in doubt, start with a smaller engagement to test a firm’s quality. Many providers offer fixed scope package deals for initial pentests. Check if they offer follow up retesting or support DeepStrike, for instance, includes free retesting for 12 months in its model.

FAQs About UK Cybersecurity Companies

• Which UK cybersecurity companies are considered the largest or most prominent?

In terms of scale and reputation, NCC Group FTSE 250 and BAE Systems Applied Intelligence part of BAE Systems are among the largest UK cybersecurity providers. NCC has been operating for 30+ years, and BAE’s cyber arm leverages defense level expertise. Both serve major banks and governments. Other high profile firms include Pen Test Partners, Redscan now part of Kroll, and Darktrace, an AI driven detection company.

• What services do these top companies typically offer?

Most leading UK firms provide penetration testing web, network, mobile, cloud, red teaming simulated attacks, and often managed detection and response MDR/SOC. For example, NCC Group and Pen Test Partners focus on deep technical pen tests and threat led engagements, while Redscan/Kroll emphasizes 24×7 MDR. Firms like Bridewell and Nettitude also bundle compliance consulting ISO, GDPR, PCI with their security testing.

• Why are accreditations like CREST important?

CREST and NCSC CHECK accreditations mean a company meets rigorous standards for security testing. They indicate the testers have been certified and follow best practices. Most top UK pen test firms NCC, PTP, Secarma, etc. hold CREST accreditations, which reassures clients of quality and reliability. If your organization is in a regulated sector finance, defence, CREST/CHECK is often required.

• How much do cybersecurity services cost in the UK?

Costs vary widely. Larger consultancies often charge premium day rates for bespoke projects especially for enterprise scale assessments. Boutique firms and SMB focused providers like Bulletproof or Secarma’s packaged PTaaS may offer fixed prices for defined scopes. Factors include scope complexity, company size, and delivery model. For example, a basic web app pentest might run a few thousand pounds, whereas a multi week red team exercise could be tens of thousands. It’s best to get quotes tailored to your needs.

• Are there UK cybersecurity companies for small businesses?

Yes. While many big firms target large clients, several focus on SMBs and startups. Bulletproof, DeepStrike, and Redscan Kroll offer more accessible packages. They provide rapid turnarounds and affordable options to comply with standards like PCI or ISO. Additionally, firms like Bridewell with MS Azure solutions and Redscan’s Kroll Responder are popular with mid market companies. Always look for services labeled “SME friendly” or fixed scope deals.

• What is MDR vs MSSP, and why does it matter?

MDR Managed Detection and Response and MSSP Managed Security Service Provider are often used interchangeably, but MDR specifically focuses on threat detection and rapid incident response, whereas MSSP can cover broader security management like firewalls, VPNs. In the UK market, Redscan, Bridewell, and NCC offer MDR solutions. Knowing the difference helps when choosing a provider to ensure they meet your monitoring and response needs.

• How do UK cybersecurity companies handle deepfake or AI threats?

Many top firms are incorporating AI into both attacks and defenses. While not all specialize in AI security, firms like NCC Group and BAE have research teams addressing AI powered threats. External sources note that UK leaders are investing in AI governance. For example, IBM’s research highlights AI’s role in breaches, and UK companies are beginning to offer AI governance services. If AI/deepfake risk is a concern, look for providers that mention AI driven attack simulation or defenses in their service descriptions.

Cyber threats in 2025 demand more than awareness, they demand action. Top UK cybersecurity firms from legacy consultancies like NCC Group and BAE Systems to agile specialists like DeepStrike and Secarma offer a range of services to match your risk profile. The key is finding the right partner: one with proven expertise in your industry, recognized accreditations, and a service model that fits your pace.

Ready to Strengthen Your Defenses? If you're looking to validate your security posture and uncover hidden risks, DeepStrike is here to help. Our team of seasoned pentesters and security architects provides clear, hands on guidance to protect your business.

Explore our Penetration Testing Services to see how we can proactively find vulnerabilities before attackers do. Drop us a line we’re always ready to dive in.

About the Author

Mohammed Khalil is a Cybersecurity Architect at DeepStrike, specializing in advanced penetration testing and offensive security operations. With certifications including CISSP, OSCP, and OSWE, he has led numerous red team engagements for Fortune 500 companies, focusing on cloud security, application vulnerabilities, and adversary emulation. His work involves dissecting complex attack chains and developing resilient defense strategies for clients in the finance, healthcare, and technology sectors.