The verdict in three sentences
A web application security audit in London costs, in 2026, between 4,000 and 15,000 EUR depending on scope: pentest only, full OWASP audit, or audit with remediation. Monitoring and a WAF add 100 to 500 EUR/month. Securing before scaling costs a fraction of a data breach, which combines technical, legal, reputational and downtime costs.
Audit types and scopes for 2026
Not all audits are equal. The choice depends on application criticality and exposure. Here are the 2026 orders of magnitude in London.
| Audit type | Scope | 2026 cost (EUR) | Timeline |
|---|---|---|---|
| Black-box pentest | External attack, no access | 4,000 - 8,000 | 1-2 wks |
| Grey-box pentest | With user accounts | 6,000 - 12,000 | 2-3 wks |
| OWASP Top 10 audit | Code + configuration | 5,000 - 10,000 | 2-3 wks |
| Audit + remediation | Fixes included | 8,000 - 15,000 | 3-6 wks |
| Cloud architecture audit | IAM, network, secrets | 5,000 - 12,000 | 2-4 wks |
| Security code review | Static + manual analysis | 3,500 - 9,000 | 1-3 wks |
For a B2B application exposed before scaling, a grey-box pentest + remediation (8,000-15,000 EUR) offers the best coverage-to-price ratio.
Continuous protection and cost of risk
An audit is a snapshot in time. Security is maintained over time with recurring measures.
| Recurring item / risk | 2026 order of magnitude | Frequency |
|---|---|---|
| Managed WAF (Cloudflare, AWS) | 100 - 400 EUR/mo | Monthly |
| Monitoring / SIEM | 150 - 500 EUR/mo | Monthly |
| Automated vulnerability scanning | 80 - 300 EUR/mo | Monthly |
| Annual re-test | 3,000 - 8,000 EUR | Yearly |
| Average SME data breach cost | 25,000 - 200,000 EUR | Per incident |
| Downtime (per day) | 2,000 - 20,000 EUR | Per incident |
In 2026, ransomware and breaches via poorly secured APIs remain the top incident causes. The continuous protection budget (often 300-800 EUR/month) is marginal against the cost of a single major incident.
Mini case study
Sophie, IT director of a B2B SaaS vendor in London, is preparing to scale from 300 to 3,000 customers. She orders a grey-box pentest + remediation at 11,500 EUR, then puts in place a WAF + monitoring at 380 EUR/month (4,560 EUR/year). First-year budget: 16,060 EUR. The audit reveals an injection flaw giving access to every account's data. The estimated cost of a breach affecting 3,000 customers (notifications, legal, churn) exceeded 90,000 EUR: the audit alone pays for itself immediately.
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FAQ
What is the difference between a pentest and an OWASP audit?
The pentest simulates a real attack to find exploitable entry points (4,000-12,000 EUR). The OWASP audit methodically checks the 10 major risks across code and configuration (5,000-10,000 EUR). Ideally you combine both.
How much is a WAF for a B2B application?
Between 100 and 400 EUR/month for a managed solution (Cloudflare, AWS WAF), depending on traffic and rules. Monitoring/SIEM adds 150 to 500 EUR/month.
How often should an audit be repeated?
An annual re-test (3,000-8,000 EUR) is recommended, plus an audit at every major architecture change or before significant scaling.
What is the real cost of a data breach for an SME?
Between 25,000 and 200,000 EUR depending on data volume and sector: notifications, forensics, legal advice, customer loss and possible GDPR fines. Downtime adds 2,000 to 20,000 EUR per day.
How long does a full audit take?
Between 3 and 6 weeks for an audit with remediation, including testing, a prioritised report and verification of the fixes.
Let's scope your project. Tell us about your application (technology, exposure, user volumes) and your budget so we can frame the right audit scope. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
