Beyond the Balance Sheet: Building Cyber Resilience in Accountancy
The evolving nature of financial data, remote collaboration, and cloud adoption has fundamentally reshaped how the accountancy profession operates.
The UK accountancy sector has become one of the most continually targeted industries in the cyber threat landscape. Accountancy firms - from “Big Four” practices to local auditors and outsourced bookkeeping providers, hold a unique position of trust. Processing and storing vast amounts of financial, payroll, tax, and personally identifiable data, making them high-value targets for financially motivated threat actors and nation-state groups alike.
As threats evolve, so too must defences. Yet recent studies reveal persistent challenges:
Only 30% of firm leaders believe their organisation’s compliance programme is adequately supported by modern technology and investment.
Just 29% strongly agree that their governance framework can effectively oversee and manage cyber risk.
Over 70% of leaders anticipate a rise in financial crime and cyber risk in the coming year.
Meanwhile, 61% of executives cite the increasing use of AI by criminals as a major catalyst for escalating threat exposure.
In this environment, the importance of cyber security becoming a valued,strategic, board-level issue is greater than ever before. Firms that fail to embed cyber resilience into their operational strategy not only risk financial loss but reputational erosion and regulatory scrutiny.
The Most Significant Cyber Threats Facing UK Accountancy Firms
1. Ransomware and Double Extortion
Ransomware remains the most severe operational risk. Modern campaigns no longer rely solely on file encryption, instead combining data theft, extortion, and reputational coercion, making it nearly impossible for firms to quietly recover from an attack.
Attackers frequently target accountancy systems during fiscal deadlines or audit seasons, leveraging the criticality of access to client data. Threat groups such as Akira, RansomHub, and LockBit have shifted towards exfiltration-first operations, stealing sensitive audit files, tax documentation, and payroll data before issuing ransom demands.
Common entry points include:
Compromised remote desktop services or VPNs without MFA.
Phishing emails distributing malicious payloads disguised as invoices or tax correspondence.
Insecure third-party integrations and document-sharing portals.
The average cost of a ransomware incident in financial and professional services exceeded £3.5 million in 2025, factoring in downtime, recovery, and reputational damage.
PureCyber’s Response:
Our MXDR platform provides real-time detection of lateral movement, privilege escalation, and data exfiltration attempts - enabling rapid containment before encryption or data theft occurs.
2. Business Email Compromise (BEC) and Financial Manipulation
BEC remains one of the most profitable forms of cyber crime. Unlike malware, these attacks exploit human behaviour and trust. By compromising or spoofing trusted accounts, threat actors divert legitimate payments or intercept confidential communications between clients and accountants.
Emerging 2025 trends include:
Deepfake audio of firm partners authorising payments.
AI-enhanced social engineering, using language models to craft highly contextual messages.
Multi-stage attacks where adversaries monitor communications for weeks before altering bank details or intercepting invoices.
In one case investigated by PureCyber, a mid-sized firm lost over £240,000 after a partner’s mailbox was compromised via a stealer log found on the dark web. The attackers monitored conversations with clients and modified payment instructions at key points.
3. Supply Chain and Cloud Platform Vulnerabilities
Accountancy has rapidly migrated to the cloud - platforms like Xero, Sage, QuickBooks, and Microsoft 365 now underpin most client operations. Yet this shift introduces significant supply chain dependencies.
In 2025, multiple UK firms experienced exposure due to:
Compromised plug-ins or API connectors between accounting platforms and CRM tools.
Third-party payroll processors suffering breaches that cascaded through client ecosystems.
Insecure cloud storage permissions, leading to inadvertent leaks of client records.
Supply chain incidents often go undetected for weeks - leaving firms accountable under data protection laws despite the root cause lying with a vendor.
PureCyber’s approach includes ongoing third-party risk assessments, dark web monitoring for leaked credentials, and contractual guidance to ensure vendors adhere to the same cyber maturity standards.
4. Credential Theft and Dark Web Exposure
Credentials remain the currency of cyber crime. In 2025, 80% of phishing campaigns targeted credential harvesting, primarily through cloud services like Microsoft 365 and Google Workspace. Even more concerning, 4/5 of phishing websites now use HTTPS - making them appear legitimate to unsuspecting users.
Once stolen, these credentials often surface in stealer logs or are sold on the dark web.
Attackers then leverage them for:
Account takeovers and data exfiltration.
Initial access into corporate networks.
Secondary attacks on client systems using shared credentials.
PureCyber’s threat intelligence team routinely identifies exposed accounts belonging to UK accountancy firms within days of compromise - demonstrating the need for continuous credential monitoring and automatic session revocation.
5. Insider Risk and Data Leakage
Insider threats, both intentional and inadvertent - remain a consistent challenge in the accountancy sector.
Staff members with extensive access to financial systems or client data can unintentionally expose sensitive information through email forwarding, personal device use, or cloud misconfigurations.
Conversely, disgruntled employees or contractors may deliberately extract client lists or payroll data before departure.
In 2025, insider data leakage accounted for an estimated 22% of all reported data breaches within the professional services industry.
Embedding user behaviour analytics, least-privilege access policies, and proactive offboarding controls can dramatically reduce exposure.
6. Emerging Threat: AI-Powered Fraud and Synthetic Identities
AI has become a dual-use tool in cyber crime. Attackers now use AI to:
Generate fake invoices indistinguishable from legitimate ones.
Forge synthetic client identities that can pass basic AML or KYC checks.
Create deepfake voice calls or video messages impersonating senior partners.
As AI-generated deception grows, firms must adopt AI-enabled detection and verification tools capable of authenticating voice, image, and behavioural anomalies in communications.
Building Cyber Resilience in the Accountancy Profession
Resilience isn’t achieved through technology alone. It’s built through a comprehensive, integrated approach combining governance, human expertise, and technical control.
To remain compliant, competitive, and secure, accountancy firms must embed cyber security into their strategic and operational DNA.
Key Principles of Cyber Resilience:
1. Adopt a Zero-Trust Mindset:
Assume breach and verify every user, device, and connection - internally and externally.
2. Layered Defence Architecture:
Integrate firewalls, endpoint detection and response (EDR), and cloud-native monitoring tools to provide full visibility across hybrid environments.
3. Harden Against Credential Abuse:
Enforce phishing-resistant MFA, password managers, and continuous identity verification.
4. Vendor Governance:
Review supplier contracts, audit their security posture, and enforce breach-notification clauses.
5. Data Backup and Recovery:
Maintain offline, immutable backups and regularly test restoration procedures to ensure operational continuity.
6. Awareness and Culture:
Conduct continuous, role-based training and simulate social engineering attacks to build muscle memory against deception.
7. Governance and Incident Response:
Establish board-led oversight, with defined playbooks for 72-hour breach notification and regulatory engagement (ICO/FCA alignment).
Creating a Safer Digital Future for Accountancy
The UK accountancy sector faces a complex and continually evolving cyber threat landscape - from ransomware and phishing to insider risks and AI-enabled fraud. Yet defences across the profession remain inconsistent, leaving many firms exposed.
By prioritising cyber resilience, strengthening governance, and investing in modern security technologies, accountancy firms can protect their clients, their reputation, and the integrity of the profession as a whole.
Firms that embrace cyber resilience as a strategic business function will not only safeguard their operations but also gain a competitive advantage in an increasingly regulated and digital economy.
PureCyber’s comprehensive service stack is designed to empower financial institutions to address these challenges head-on, combining advanced detection, proactive threat intelligence, and expert-led defence to protect your clients, data, and reputation:
From 24/7 Security Operations Centre (SOC) monitoring to threat intelligence, penetration testing, and supply chain risk management, our services provide the layered protection needed to stay ahead of cyber criminals. We also deliver compliance support and awareness training, ensuring your teams remain informed and resilient against emerging threats. In a sector reliant on trust and integrity, a strong cyber security posture is a foundational part of building that reputation.
How Can PureCyber Help?
The PureCyber team are here to take over the burden of your cyber security and ensure your organisation’s data remains secure and well managed, with proactive monitoring and real-time threat intelligence - providing you with a comprehensive and reliable cyber department to support you in all aspects of your security efforts, including: 24/7 Security Operations Centre (SOC) services, MXDR (Managed Extended Detection & Response),Threat Exposure Management (TEM) & Brand Protection Services & Penetration Testing.
PureCyber is recognised as an Assured Service Provider by the NCSC to offer governance and compliance consultancy services/audits. Contact our team of compliance experts to enquire about our full range of Governance Support - including Cyber Essentials, ISO 27001, FISMA, SOC1 and SOC2 standards.
Get in touch or book a demo for more information on our services and how we can safeguard your organisation with our expert cyber security solutions.
Email: info@purecyber.com Call: 0800 368 9397