Penetration Testing for Accountants and Accounting Firms in the UK

Penetration testing for accountants and accounting firms in the UK

Accounting firms sit at the intersection of two things attackers value most: sensitive financial data and trusted relationships with businesses. A compromised accounting firm does not just expose its own data — it provides a pathway into the financial records, bank accounts, and tax information of every client it serves.

Why accounting firms are targeted

The financial data held by accounting firms is immediately valuable. Tax returns contain detailed income information. Management accounts reveal business performance and bank account details. Payroll records include personal information for every employee of every client.

Business email compromise targeting accounting firms is particularly lucrative. Attackers who gain access to an accountant's email account can monitor correspondence, wait for the right moment, and instruct clients to redirect payments to fraudulent bank accounts.

The regulatory context

Accounting firms are subject to UK GDPR, HMRC's Making Tax Digital requirements, and professional body standards from ICAEW and ACCA — all of which include security obligations.

Common vulnerabilities

Client portals with weak authentication. Email security gaps leaving the domain open to spoofing. Outdated software in accounting applications. Weak passwords on client-facing systems.

How much does it cost

Traditional penetration testing costs £5,000 to £15,000. For smaller practices, Yrzo AI offers automated penetration testing at £399 per scan — 44 security checks with a plain-English report and evidence of due diligence for regulatory purposes.