September 14, 2025
Compare the top UK penetration testing providers in 2025 DeepStrike, NCC Group, and more. Learn costs, CREST certifications, and how to choose the right vendor.
Mohammed Khalil
Penetration testing companies in the UK specialize in ethical hacking services that simulate real attacks on your systems to find vulnerabilities. In other words, they hack you before the bad guys do, so you can fix weaknesses first. In 2025, demand for these services is higher than ever. Why? Because cyber threats are constantly evolving nearly 43% of UK businesses experienced a cyber attack or breach in the past year.
High profile incidents like a £300 million attack on a UK retail chain underscore that even well defended organizations are at risk. Penetration testing isn’t just nice to have, it's become essential for UK companies to validate their security posture, meet standards like ISO 27001 and PCI DSS, and protect customer data from breaches.
If you’re researching the best pen testing companies in the UK, this guide has you covered. We’ll explain what penetration testing involves, why it matters for 2025 threats, how to choose a qualified vendor hint: look for CREST certification, what a typical penetration testing cost in the UK looks like, and who the top providers are in the UK market. By the end, you’ll know how to find the right partner to strengthen your defenses whether you’re a small fintech startup or a large enterprise needing advanced red teaming.
Let’s dive in!
Penetration testing or pen testing is essentially hiring good guy hackers to attack your systems under controlled conditions. The goal is to identify security weaknesses before malicious actors do. A formal definition from NIST describes pen testing as security testing in which evaluators mimic real world attacks in an attempt to identify ways to circumvent the security features of an application, system, or network. In practical terms, that means skilled ethical hackers use the same tools and techniques as cybercriminals to probe your defenses but with permission and for your benefit.
During a penetration test, the testers will try to exploit any vulnerability they can find: outdated software, misconfigured servers, weak passwords, missing patches, logical flaws in applications, you name it. Unlike automated scanners, a real pen test is highly manual and creative.
Testers might chain together multiple low risk vulnerabilities to achieve a full system compromise, the kind of complex attack a real adversary would perform. At the end, the pen testers provide a detailed report showing how they broke in, what data they accessed, and clear remediation steps to fix the issues.
Not all pen testing providers are created equal. Choosing a partner to trust with your security testing is a big decision. You need skilled testers who will do a thorough job, communicate well, and respect your systems.
No one wants a pentester accidentally crashing a production server with an uncoordinated scan!. Here are some key factors and tips for selecting the best penetration testing company in UK for your needs:
1. Look for Industry Certifications and Accreditations: In the UK, one of the strongest indicators of a reputable provider is CREST certification. CREST Council of Registered Ethical Security Testers is an industry body that certifies companies and individuals for quality of penetration testing.
Engaging a CREST certified penetration testing company means the firm has passed rigorous assessments and adheres to high standards. Similarly, if you need government work done, look for CHECK accreditation NCSC’s scheme for government suppliers. Individual team certifications matter too: OSCP, OSWE, CREST CRT/CCT, CISSP, GIAC GPEN/GXPN, and others demonstrate the testers have proven skills.
For PCI testing, having a QSA or PCI certified consultant involved can be a plus. In short, ask about the team’s qualifications. Top UK firms will be happy to share their credentials and might even assign certified individuals to lead your test depending on compliance needs. For example, an ISO 27001 test might require a CREST certified tester as evidence.
2. Experience and Specialization: Consider the provider’s track record, especially in your industry or technology stack. If you’re a financial services firm, you may prefer a company that has done lots of work in finance and understands things like core banking systems or SWIFT networks.
If you’re heavy on cloud and DevOps, maybe lean toward a firm known for cloud pen testing. Some companies specialize e.g., one might be known for web app testing excellence, another for hardware/IoT testing.
Ask for case studies or client references in your vertical. An important aspect is how long they’ve been around and their team size; an established firm some like NCC Group or BAE have decades of history brings a wealth of tested methodology. Newer boutique firms like some startups might be more agile or innovative; it's a trade off.
The UK has both global large providers and smaller expert boutiques. If you need a broad, ongoing partnership, a larger firm with multiple services might suit you. If you need a one off deep test on a specific app, a niche expert consultancy could be great.
Either way, ensure they have first hand experience with the threats you’re concerned about for example, have they done a red team engagement similar to what you’re looking for, or tested an app with millions of users, etc..
3. Methodology and Scope Definition: A good penetration testing company will be very clear about how they scope and conduct the test. Be cautious of any vendor that gives you a quote without asking detailed scoping questions.
Proper scoping number of apps, IPs, user roles, credentials provided, etc. is crucial to get a realistic quote and outcome. If a vendor doesn’t inquire about your environment and just offers a fixed price package blindly, that’s a red flag you might end up with a shallow test.
Reputable providers will outline their methodology: typically steps like Reconnaissance, Threat Modeling, Vulnerability Analysis, Exploitation, Post exploitation, and Reporting. often aligning with guidance from OWASP or NIST SP 800-115 They should use a mix of automated tools and manual techniques.
Don’t hesitate to ask what tools they use or request a sample report. A sample penetration testing report, even a sanitized one will show you the depth of findings and clarity of recommendations. High quality reports are comprehensive and actionable, not just scanner printouts.
Also, check if they include a debrief session and remediation support. The best companies will walk you through findings and answer your dev team’s questions on how to fix issues. Some even offer a free retest of vulnerabilities after you patch them. DeepStrike, for example, includes free unlimited retesting of findings to verify your fixes.
4. Service Range and Support: Depending on your needs, you might prefer a provider that can be a one stop shop. Many penetration testing companies in the UK also offer related services like vulnerability assessments, continuous monitoring, incident response, or training.
If you foresee needing those, consider a firm that provides them so it could streamline things. Additionally, check their availability and flexibility.
Are they booking tests 2 months out common with some in demand firms or can they start next week? Do they offer testing outside of UK hours if you have global operations? Also, language matters if you need a report in both English and maybe a local language for subsidiaries, ask.
UK providers primarily operate in English but many have international teams. Lastly, consider if you want a local presence: some companies have offices in London, Manchester, etc., which can be handy for on site testing or just peace of mind that they understand the UK context.
Others operate remotely just fine. In today’s remote world, you can certainly hire a top firm from anywhere, but some UK organizations feel more comfortable with a provider that’s UK based for legal/data protection reasons or simply ease of communication.
5. Cost and Value: We’ll dive into penetration testing cost next, but when choosing a vendor, it’s wise not to simply take the cheapest quote. In cybersecurity, you often get what you pay for. Super low quotes suspiciously cheaper than others could indicate the test will mostly be automated or that the provider lacks experience.
On the other hand, the most expensive quote isn’t always the best either, some might overscope or upsell. The key is value: a thorough test that fits your budget and gives actionable results.
When comparing proposals, look at how many days of testing are included, the team composition are senior consultants involved or just juniors?, and whether things like a follow up retest are included.
A fair pricing model should align with the effort and expertise provided. And remember, a penetration test is an investment in preventing costly breaches. Spending £10k on a test may save you millions by avoiding a data breach or ransomware incident. Many providers will work with you to prioritize critical targets if the budget is limited for example, testing your most exposed assets first.
Also, consider establishing a long term relationship. Some firms offer discounts or flexible pricing if you plan ongoing engagements like multiple tests a year or multi year contracts.
Quick Tip: Create a checklist when evaluating vendors. Include things like: CREST certified? How many years of experience? Sample report quality? References available? Retest included? Methodology documented? By asking similar questions to each, you can objectively compare. We even wrote a guide on questions to ask penetration testing companies feel free to use it to grill prospective providers!
Finally, trust your gut to an extent you’ll be working closely with this team, possibly under time pressure, so you want people who communicate clearly and professionally. The pre-sales interactions can be telling; if they are responsive and thoughtful now, likely they’ll be great during the test. If they are slow or pushing a cookie cutter approach, maybe not the best fit.
One of the first questions organizations ask is: How much does a penetration test cost in the UK? The answer is it depends primarily on scope and complexity but we can certainly discuss typical pricing to give you a ballpark.
Pricing Models: Most penetration testing companies charge either a fixed fee per engagement or more commonly a day rate for the consultants. In the UK, day rates for manual penetration testing generally range from £800 to £2,500 per day depending on the provider and the expertise level required.
An average rate for a thorough test by a certified professional is often around £1,200/day. This rate might be higher for specialized work e.g., testing a very complex environment or a rush engagement or lower if you negotiate for a volume of work like a 20 day project might get a slight discount per day.
Typical Total Costs: The total cost = day rate * number of days. How many days a test takes will depend on scope. A small test says a single simple web application or a small office network might be scoped at 3-5 days of testing.
That could cost on the order of £3,000- £7,000 as a rough estimate. A large test like a comprehensive test of multiple apps, networks, and a cloud environment for a mid size company could be 15-20 days of effort, costing £15,000- £30,000 or more.
Very extensive engagements or full red team simulations over weeks can run into the high tens of thousands. According to one UK pricing guide, a typical fair pen test day rate is £1,200 and if you get a quote for £25k, that implies roughly 20 days of work being planned.
Always look at how the provider scoped the days one might quote 5 days for a test while another says 10 days for the same scope. If one quote is significantly lower, check if they underestimated the scope or plan to use more automation.
Factors Influencing Cost:
For instance, the cost of a web application penetration testing will scale with how many pages, features, and user roles need to be tested. A small app might take 3 days; a complex one could take 15+ days.
However, white box might cover more ground at the same time. If you require exploitation of vulnerabilities to prove impact most do, that can add time versus just identifying vulns. Manual testing is time intensive but yields better results than automated scans; this is what you’re paying for.
If someone offers a super cheap test, verify that it’s not just a vuln scan. A real pen test can’t be done in a couple hours; be wary of quotes that seem too good to be true like a £500 penetration test that’s likely just a scan report.
This will increase cost but might also find more issues. It’s worth discussing with the vendor for example, you might do a mix: a senior lead tester for oversight and a couple of junior testers for breadth, to balance cost and coverage.
On site days might be billed a bit higher or with expenses. Typically, try to arrange remote testing if possible for cost efficiency but ensure a secure way for them to test jump boxes, etc., should be arranged with your IT.
For a small business in the UK, penetration testing can be made affordable by limiting scope to the most critical assets. Some companies offer fixed price packages for startups or SMBs for instance, testing one cloud hosted web app and an external scan for a flat fee. You might find offerings in the £3k 5k range targeted at small companies.
While it’s still an investment, considering the cost of a breach, IBM's data shows the average cost of a small business breach is over $3 million, which would be catastrophic. So from a risk perspective, a few thousand pounds annually for a pen test is well justified. Additionally, as mentioned, having a penetration testing report can win you business or satisfy cyber insurance, giving some ROI beyond just security.
Cost Example: Let’s say you run a mid sized e commerce business in London. You want a pen test of your public website with user accounts and payment functionality and an internal network test of your corporate office.
A possible scope might be: black box web app test with one authenticated user role 7 days; external network test 20 IPs 2 days; internal network test on site, one location 5 days. In total 14 days of work. At £1,000/day, that’s about £14,000.
The provider would deliver findings on SQL injection, XSS, any payment process issues on the web side, and things like open ports or weak AD credentials on the internal side.
You’d get a full report and maybe a free follow up test after you fix the critical items. This £14k might sound high, but if it helps you avoid a data breach that could easily cost ten times more in fines and damage, it’s a smart spend. Now, if that same company only cared about the web app, they could scope just that for 7 days and £7k as a smaller engagement.
Budgeting Tips: It’s a good idea to budget for penetration testing annually or more frequently for critical apps. Many UK businesses align pen testing with their fiscal year or project go lives. For new systems, budget a pen test before launch.
For ongoing, include it in your security budget. Keep in mind, if you’re doing it for compliance with PCI, ISO, you have to maintain that schedule and possibly show evidence like pen test reports or certificates of engagement.
Also, consider the remediation costs fixing the findings might require developer time or new tools. So plan resources for that phase as well.
One more thing: after a test, you might want to bring the same firm back to verify all fixes for the retest. Many include one round free within X days. If not, you might pay a smaller fee for a retest.
Ensure you clarify that during scoping do you include a retest of findings once we patch?. Most quality providers do, as they want to ensure their clients actually close the holes.
To sum up, penetration testing isn’t cheap, but UK market prices have become fairly standardized and competitive. You should expect to invest a few thousand pounds at minimum for a credible test.
If someone offers to do it for £500, they’re not doing a real pen test. On the other hand, the most expensive quote isn’t automatically the best; evaluate what you get for the cost.
By scoping smartly and choosing a reputable company, you’ll get the best value meaningful security insights that protect your business and far outweigh the upfront cost.
Note: Many providers, including DeepStrike and others, have startup programs or allow spread payments to make it budget-friendly. Don’t hesitate to discuss budget constraints with providers. Many will tailor something for you.
The UK is home to many cybersecurity firms offering penetration testing services from big international companies to specialized local consultancies. Here we highlight 10 notable penetration testing companies in the UK including DeepStrike known for their expertise, services, and trusted reputations. This list isn’t exhaustive there are certainly more great firms out there, but these are among the top options when looking for quality pen testing in the UK:
DeepStrike is a leading cybersecurity firm specializing in human powered, high quality penetration testing. Founded in 2016, DeepStrike has quickly grown into a premier provider by focusing on real world attack simulations and manual testing excellence.
Their team of world class ethical hackers conducts comprehensive assessments across web applications, networks/infrastructure, mobile apps, and cloud environments. DeepStrike is known for delivering very actionable, detailed reports that include proof of concept exploits and clear remediation steps.
They emphasize tailoring each engagement to the client’s threat model, rather than a checklist approach. Clients often praise DeepStrike’s thoroughness and the way they go beyond automated scans to find issues others miss.
The company holds multiple certifications; their team includes OSCP, OSWE, CISSP, etc., and the firm is pursuing CREST accreditation. DeepStrike also offers a modern PTaaS platform for continuous testing, providing real time dashboards for clients. With offices in the UK and globally, they service startups to Fortune 500s.
If you’re looking for a provider that combines deep technical expertise with flexibility and top notch client service, DeepStrike is a strong choice for full disclosure.
Example: DeepStrike often highlights success stories where their approach made a difference. For instance, in one engagement for a mid-sized fintech company in London, DeepStrike’s team uncovered a misconfigured VPN gateway and an outdated firewall rule that allowed an attacker to pivot through the network.
The client’s previous scan-based assessment had missed these issues, but DeepStrike’s OSCP-certified testers exploited them to demonstrate how an attacker could access sensitive customer data.
The DeepStrike team provided immediate remediation guidance and, after fixes were applied, performed their free unlimited retesting to confirm all vulnerabilities were resolved. This proactive test not only prevented a potential breach but also helped the client pass a subsequent compliance audit with flying colors.
NCC Group established 1999 is one of the heavyweights in cybersecurity, with a major presence in the UK. They are a CREST member and have a global team of certified professionals focusing on manual, in depth penetration testing across infrastructure, cloud, and applications.
NCC Group’s experience is hard to beat; they've seen it all, working with governments, banks, and enterprises worldwide. In the UK, they’re often the go to for large or high assurance projects that demand rigorous testing and a proven methodology.
Their services span everything from network and web app testing to hardware/IoT and even physical security assessments. NCC is also involved in research and publishes advisories, which speaks to their expertise.
While they may come at a premium price, you get what you pay for: thorough testing and a trusted name. They also have the advantage of a large pool of specialists to draw from for any niche skill RF testing? SAP testing? They likely have someone.
Pentest Limited is a UK based specialist firm founded 2001, headquartered in Manchester. As their name suggests, penetration testing is their core focus.
They are a CREST accredited company and have over two decades of experience in uncovering vulnerabilities for clients. Pentest Limited offers services spanning web application testing, network/infrastructure testing, mobile app testing, and social engineering.
They’ve earned a strong reputation for quality winning industry awards for their work and they boast high customer satisfaction ratings. Being a smaller specialist, Pentest Limited is often praised for its personalized approach.
Their team spends ample time understanding client needs and is known to be very thorough in execution. If you’re looking for a well established UK pen testing boutique with deep expertise and not necessarily needing a big brand name like NCC, Pentest Limited is a top contender.
Rapid7 is actually an American headquartered company, but it has offices in the UK and a significant UK client base. Known broadly for their security products Nexpose, Insight platform, etc., Rapid7 also provides penetration testing services via their global consulting arm. They combine automation with manual testing effectively.
Rapid7’s consultants can assess networks, web/mobile apps, and cloud environments, often leveraging the company’s own tools for efficiency. They are commended for comprehensive reports and a responsive support team.
One advantage of Rapid7 is if you are already using their solutions like InsightVM for vuln management, the pen test results can integrate into that ecosystem. They have experience across many industries and threat scenarios.
Being a large firm, they can handle big projects or simultaneous tests. However, you’ll want to ensure the individual consultants on your project have the right expertise, as quality can vary.
Overall, Rapid7 is a solid choice, especially for those who want a mix of manual testing backed by cutting edge technology and don’t mind a more corporate provider.
Nettitude is a UK based cybersecurity consultancy founded 2003, part of Lloyd’s Register LRQA known for its rigorous approach. They are CREST approved and also hold CHECK status. Nettitude offers penetration testing across cloud, network, application, and IoT, and they’ve made a name providing actionable insights and helping clients maintain strict compliance.
Clients often note Nettitude’s professionalism and thorough reports, as well as their proactive recommendations for security improvements. They also do red teaming and managed security services, but pen testing is a key pillar. Nettitude has worked with various sectors, from finance to marine to government, which speaks to versatility.
If you seek a reputable UK consultancy that combines technical skill with an understanding of compliance PCI, ISO, etc., Nettitude should be on your shortlist.
Bulletproof is a UK cybersecurity firm that provides a full suite of testing services. They are CREST certified and offer penetration testing for web apps, networks, cloud, and more, to businesses of all sizes.
Bulletproof emphasizes a compliance focused approach, often helping clients in regulated industries meet requirements they focus on GDPR, ISO 27001, and other standards in their testing methodology.
They’re also known for quick turnaround and affordable packages tailored to SMEs, making them a popular choice among UK small and mid market companies that need pen tests for Cyber Essentials Plus or similar.
Bulletproof’s reports are detailed yet understandable, and they provide guidance through the remediation process. They have offices in London and beyond.
Trustwave is a global security company with a UK presence under Trustwave SpiderLabs, their elite testing division. Trustwave SpiderLabs offers high grade penetration testing services in the UK, alongside managed security services and incident response expertise.
They are known for having some really seasoned testers and researchers on the team. SpiderLabs has been involved in uncovering major vulnerabilities they often present at conferences like Black Hat.
For pen testing clients, this means you get testers who have seen advanced attack techniques. They can test networks, apps, cloud and often are brought in for challenging environments.
SpiderLabs is also CREST certified for pen testing and STAR simulated targeted attack services. Clients note that the SpiderLabs team is proficient in handling incident response and vulnerability management as well, giving an end to end security partner vibe.
Engaging Trustwave SpiderLabs might be ideal if you want a globally recognized team with deep expertise for example, if you suspect you need adversary simulation that goes beyond a basic pen test. Do note, being part of a big company, their processes are formal and ensure you align on scope to get the bespoke attention you need.
Secarma is a UK based penetration testing and red teaming specialist headquartered in Manchester, established 2001. They are CREST accredited and known for an offensive security focus.
Secarma provides expert pen testing across web, mobile, infrastructure, and also conducts full scale red team exercises. They have experience protecting clients in high risk sectors like healthcare and finance.
In fact, Secarma often highlights their work in healthcare and finance, where they simulate real world attacks to uncover security weaknesses. They’re praised for professionalism and a thorough approach. Essentially, they don’t quit until they’ve checked every possible door and window in your cyber defenses.
Secarma also offers a Penetration Testing as a Service PTaaS platform for continuous testing, catering to organizations that want ongoing assurance. If you want a UK provider that will really think like a determined attacker and perhaps run multi-faceted engagements including social engineering, etc., Secarma is a strong choice.
BAE Systems Applied Intelligence is the cybersecurity arm of BAE Systems, the big defense contractor. With that pedigree, it’s no surprise they deliver top notch services.
BAE’s security consulting division in the UK offers advanced penetration testing and threat intelligence, often serving government, defense, and critical infrastructure clients. They bring a defense grade security approach, meaning very high thoroughness and an understanding of nation state level threats.
Their experts frequently work on securing military or government systems, and that expertise translates into robust testing practices for any client. BAE is also involved in developing security tools and research they’ve been known to be ahead of the curve on threat trends.
If you are an organization that requires the utmost assurance perhaps in sectors like finance, energy, or public sector BAE AI is a top tier option. They are trusted by governments worldwide, which speaks volumes.
The trade off is they might be pricier and have longer lead times due to demand. But when you absolutely need the best and to impress stakeholders that yes, we had BAE test our security, they’re a go to in the UK.
SecureWorks is a global cybersecurity firm with an office in London. They’re known for managed security services, but they also have a strong penetration testing and adversary simulation team.
SecureWorks brings the benefit of advanced threat intelligence and analytics tech from their broader operations into their testing engagements. They have a worldwide team, which can be an advantage if you have global operations to test they can coordinate across regions.
SecureWorks’ pen testing services cover network, application, and cloud assessments, and they often tie findings into their managed detection & response advice. Clients often commend SecureWorks for their advanced threat knowledge e.g., they might simulate the tactics of known threat groups that target your industry, giving a realistic assessment.
They’re also very used to working with enterprises, so they handle big environments well. As part of Dell, they have corporate robustness with a consultant’s skillset. If you’re already using SecureWorks for SOC or MDR, it’s logical to consider them for pen testing too, as it integrates nicely, findings can feed into improving monitoring, etc..
Even if not, they’re a reputable choice, especially for those wanting a large provider backing the engagement.
Each of the companies above has a proven track record in the UK for delivering quality penetration testing. All of them cover the basics web app, network, mobile, and cloud testing but each brings its own flavor and strengths.
When choosing among them, consider factors like the certifications most of the above are CREST approved or similar, their experience in your industry, their availability, and of course pricing that fits your budget.
It’s also worth noting a few honorable mentions in the UK pen testing space: companies like Redscan, Intruder, Pen Test Partners, MDSec, 7 Elements, Context Information Security Accenture, Coalfire with UK branch, PwC Cybersecurity, and others all offer reputable services.
The UK has a rich ecosystem of providers, so you’re not short on choice. Do your due diligence, and you’re likely to find a great partner.
Sources for company info: the above summaries are compiled from company websites, Clutch reviews, and industry analyses including recent top providers rankings. This ensures an independent view of each firm’s reputation and offerings.
What’s the difference between a penetration test and a vulnerability assessment?
A vulnerability assessment is an automated scan or review that identifies known vulnerabilities in your systems, typically producing a list of potential issues like missing patches or misconfigurations. A penetration test goes a step further; it involves human ethical hackers actually exploiting vulnerabilities to see how far they can get. Think of a vuln assessment as a routine security check-up, while a pen test is a full-on realistic attack simulation. The pen test validates which vulnerabilities are truly dangerous by discovering complex attack paths that automated tools might miss. For example, a vuln scan might flag “SQL Injection possible” on an app. A pen tester will attempt it, and if successful, show that an attacker could dump your database via that flaw. In practice, organizations use both: vuln scanning frequently to catch obvious issues, and penetration testing periodically for deep assurance. Bonus: Pen testers often perform a vuln assessment as a phase of the test, then manually exploit the findings.
How much does a penetration test cost in the UK?
The cost can vary widely based on scope and complexity. For a typical engagement, UK companies can expect to pay roughly £800-£1,500 per day for professional penetration testing services. Small tests a few days of work might be a few thousand pounds total, while large, extensive tests multi-week projects can run into the tens of thousands. For example, a simple 3-day external test might cost £3k, whereas a 15-day multi-app test could be £1520k. Day rates also depend on the provider’s reputation and the expertise of testers; a CREST-certified firm with highly experienced staff may charge towards the higher end. Keep in mind, paying for quality is worth it: a thorough test that finds serious vulnerabilities is far cheaper than a data breach. Many firms will provide a custom quote after scoping your specific needs. It’s always a good idea to prioritize what systems are most critical to test so you use your budget effectively. See the Cost section above for more detailed insights on pricing factors.
Do we need a CREST-certified penetration testing company?
While not an absolute requirement, choosing a CREST-certified company is highly recommended in the UK. CREST certification means the provider has been evaluated for technical competence and processes. Many UK industries and government bodies recognize CREST as a mark of quality. In fact, some regulations and client contracts explicitly ask for a CREST-approved vendor. Using a CREST-certified pen tester gives you confidence that they follow industry best practices and have proven skills. That said, there are excellent boutique firms that aren’t CREST members too CREST is not the only indicator of quality, but it’s an easy one to check for. If you don’t go with a CREST member company, ensure the individual testers have strong certifications, OSCP, etc. and solid references. For most organizations, the safe bet is: Yes, go with a CREST-certified penetration testing company in the UK to tick the compliance boxes and ensure a baseline of trustworthiness.
How often should we conduct penetration testing?
At minimum, annually. Most standards ISO 27001, PCI DSS, etc. and best practices suggest a full-scope penetration test at least once per year. However, you should also do a test whenever there’s a significant change in your environment, say you launched a new web portal or made major updates to critical infrastructure. Many UK businesses do two tests a year: one external-facing to check internet-facing assets and one internal to check inside the firewall, or they split tests by systems. There’s a growing trend toward continuous testing not necessarily full pen tests every month, but more frequent targeted tests on new releases or critical systems. If you have a fast development cycle, consider Penetration Testing as a Service PTaaS where smaller tests are done on each release or on a quarterly basis. Also, certain compliance regimes have specific frequencies: PCI DSS requires annual tests and after significant changes; some cyber insurance policies might want quarterly vulnerability scans plus annual pen tests. Ultimately, the frequency should match your risk profile if you’re in a high-target industry finance, healthcare, etc., more frequent testing is justified. If you’re a small, low-profile business, annual is usually fine. Regularity is key: schedule it in advance so it doesn’t fall by the wayside, and combine it with a plan to remediate findings promptly.
Will penetration testing disrupt our operations or cause downtime?
A well-executed penetration test should not cause significant disruption, especially if coordinated properly. Professional testers take precautions to avoid breaking things for example, they might refrain from very aggressive exploits on production systems during working hours. That said, any test carries a small risk e.g. a scan that overloads an unstable system. To mitigate this, you and the vendor will agree on rules of engagement. You can designate critical systems that are off-limits or require special care. Many tests are done in a way that users wouldn’t notice for instance, testing a staging environment or scheduling certain steps after hours. If uptime is a huge concern, discuss a testing window or have testers avoid heavy scanning during peak business hours. In our experience, incidents are rare. Common safeguards include: monitoring systems during the test, having a direct line to stop the test if an issue arises, and doing recon/passive checks before active exploits. In summary, while a pen test is an active activity, the goal is to improve security without harming your business and reputable firms plan carefully to achieve that. It’s far more disruptive to experience a real attack than to undergo a well-planned pen test!
What happens after a penetration test?
After the testers finish their work, you will receive a report detailing all findings. This report typically includes an executive summary for management, plus technical details for each vulnerability description, impact, evidence like screenshots, and recommended fixes. Good reports also prioritize issues by severity. The next step is remediation. Your IT or development team should address the findings. Some fixes are quick change a setting, apply a patch, others might require code changes or architecture adjustments. The pen test firm is usually available for a debrief meeting where they walk through the report with you. This is a great time to ask questions and ensure you understand each issue. After fixing the critical vulnerabilities, you can often have a retest where the pen testers come back and verify that the holes are indeed closed. Many UK providers include one retest of each finding for free within a certain timeframe. Once everything is resolved, you’re in a much stronger security position! It’s wise to document the whole process if auditors or clients ask, you can show the engagement report and evidence of fixes. And then… schedule the next test down the road, because security is an ongoing journey.
Can small businesses in the UK afford penetration testing?
Yes and they really should. Cyber attacks are not only a big business problem; as noted earlier, a huge percentage of small businesses face breaches too. Many penetration testing companies offer scaled-down packages or special pricing for startups and SMBs. For example, a small business might only need a 23 day test focusing on their primary website and an external scan of their network, which could be in the low thousands of pounds. Additionally, some firms like DeepStrike and others have startup programs or allow spread payments to make it budget-friendly. The cost of not testing can be catastrophic for a small company. A single breach could put you out of business due to fines or loss of customer trust. Also, from a growth perspective, having pen test reports can boost a small business’s credibility showing investors or enterprise clients that you take security seriously. If the budget is very tight, consider at least an annual basic test on your most critical asset, and supplement with cheaper vulnerability scanning in between. In short, small businesses can’t afford not to in 2025’s threat landscape, and providers are aware of this and often adjust pricing accordingly. Shop around and don’t be afraid to discuss budget constraints with testing companies. Many will tailor something for you.
Cyber threats in 2025 are more advanced and unforgiving than ever but with the right approach, you can stay ahead of the bad guys. Penetration testing is one of your best tools for proactive defense. By regularly testing your systems with the help of skilled ethical hackers, you’ll uncover hidden vulnerabilities and fix them on your terms rather than scrambling after a breach. In the UK, we’re fortunate to have a robust selection of top notch pen testing companies that can help strengthen your security posture.
Key takeaways: focus on human driven testing automated scans alone aren’t enough, choose a reputable CREST certified provider or one with proven expertise, and make pen testing a routine part of your cybersecurity program. Whether you’re a startup looking to build customer trust or a large enterprise needing to protect millions of users, penetration testing provides that attacker’s perspective to fortify your defenses. It’s an investment that pays off in peace of mind and in preventing incidents that could cost far more.
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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.