The Importance of Cybersecurity in Accounting

Accounting firms are no longer simply the custodians of numbers; they are the custodians of some of the most sensitive information in the world. As cloud-based technology, digital transactions, and remote working have become the new norm, the accounting industry is firmly in the sights of cybercriminals everywhere. The debate is no longer whether your firm is going to be targeted; it is when.

Within this revised guide, we will delve into the true extent of the cyber threat landscape, the threats that your accounting firm in the UK is particularly exposed to, and what you can do to protect your clients, your firm, and your reputation.

The Reason Accounting Firms Are Prime Targets

It is not random chance that cybercriminals choose to target accounting firms. Your firm is targeted due to the sensitive information you possess and, historically, the level of cyber security you have invested in as compared to banks and corporations. A compromised accounting firm’s breach can result in access to:

• Client bank account details and sort codes
• National Insurance details and tax reference data
• Company financial statements and profit figures
• Payroll information including home addresses and dates of birth
• HMRC login credentials and cloud-based accounting systems

As ICAS (Institute of Chartered Accountants of Scotland) stated in 2025:

“It is not a matter of if your firm will be targeted, it is a matter of when your firm will be targeted. And the odds are stacked against your firm in the sense that it probably has already happened.”

The 5 Key Cyber security Risks in Accounting

1. Phishing Attacks

Phishing attacks are the leading threat and make up 93% of all cybercrimes in the UK’s businesses. Threat actors pose as HMRC, cloud-based software companies, and even your firm’s management team in order to obtain login credentials and/or conduct fund transfers. Phishing attacks today use Artificial Intelligence technology and are written in perfect grammar and spelling and are therefore much more sophisticated and difficult to identify than the more blatant attacks of the last ten years.

2. Ransomware

Ransomware attacks have doubled in 2025. In this type of cybercrime, attackers encrypt your company’s data and demand money in exchange for the decryption keys. What is even worse is that attackers are now stealing data before encrypting it, meaning that even after making the required payments, your clients’ data could be sold or published by the attackers. The National Cyber Security Centre in the UK has estimated that ransomware attacks could cost businesses in the UK over £1 billion annually. One notable ransomware attack in the healthcare sector in the UK was the Synovis NHS attack in 2024, which is estimated to have cost the organization an estimated £32.7 million.

3. Business Email Compromise (BEC)

In BEC scams, attackers pose as individuals in your organization, or even clients, in order to manipulate financial information. Accounting firms are especially vulnerable to BEC scams since they often have to make large financial transactions on behalf of their clients. BEC scams are getting sophisticated, with attackers waiting weeks before striking at the most opportune moment in an email thread.

4. Data Breaches via Third-Party Vendors

According to the DBIR 2025 report, also known as the Verizon Data Breach Investigations Report, third-party involvement has doubled to about 30% of all breaches. Accounting firms that utilize third-party vendors, such as cloud-based applications like payroll services, practice management tools, and document management services, automatically inherit the security flaws with these vendors. Exploitation of vulnerability as an initial breach method increased by 34% year over year, and only 54% of perimeter device vulnerability exploitation was fully remediated.

5. Human Error

One of the biggest consistencies in security breaches is not related to technology, but rather human error. Missent emails containing client information, using the same passwords across multiple platforms, and clicking on suspicious links and attachments remain some of the biggest contributors to security breaches. A recent study by Accounted 2024 reported that 22% of accounting firms admit to never testing backups, and another 22% lack fundamental documentation such as an Information Security Policy and Cyber Incident Response Plan.

6. Cloud Misconfigurations

As companies move into the world of cloud accounting, misconfigurations are creating opportunities for hackers to exploit the situation. These configurations include excessive user permissions, sharing of login credentials, and inadequate monitoring of suspicious activities. Gartner has always stated that the vast majority of cloud security incidents are the fault of the customer, not the provider.

Best Practices: Building a Cyber Resilient Accounting Firm

1. Implement Multi-Factor Authentication Immediately

Multi-Factor Authentication is a top-down, lowest-cost, highest-impact security solution, but only 40% of UK businesses are utilizing this solution at the current time. This solution prevents the vast majority of automated attacks on login credentials.

2. Regular Staff Cyber Security Training

With 43% of accounting firms offering no staff training at all, this represents a huge gap in the security posture of the accounting firm. Training should be comprehensive, including phishing, social engineering, authority, urgency, and impersonation. Simulated phishing attacks are a great way to measure the improvement in staff awareness.

3. Establish an Incident Response Plan

22% of accounting firms lack a plan for what to do in the event of a breach. An Incident Response Plan should identify who to notify, how to isolate systems, what to do with clients, and the 72-hour ICO reporting requirement. It should be practiced quarterly.

4. Utilize Encrypted and Secure Cloud Storage

Select cloud accounting and document-sharing services with end-to-end encryption, user permissions, and detailed audit trails.

5. Manage Third-Party Vendor Risks

A formal vendor security assessment is critical prior to engaging with any software or outsourcing provider. Ensure they agree to data protection obligations and ask how they handle patching and vulnerability remediation.

6. Maintain Offline Backups

Ransomware attacks are unable to access what they are unable to reach. Daily automated backups, which are stored offline or in another cloud environment, are your last defence against ransomware attacks.

7. Pursue Cyber Essentials Certification

Only 9% of accounting firms in the UK are certified to the UK Government’s recommended minimum level of security, known as Cyber Essentials. Not only does it demonstrate your commitment to security, but it may also help reduce your cyber insurance premiums and is increasingly becoming mandatory for larger clients.

Emerging Technologies Reshaping Cyber security in Accounting

AI-Powered Threat Detection

Artificial intelligence is changing the face of cyber security in accounting, both for defines and offense. For defines, AI systems are constantly analysing transactions in real-time to detect any unusual activity or suspicious login attempts. For offense, AI is making phishing attacks and social engineering attacks so believable that it is becoming increasingly challenging for human intuition to keep up.

Blockchain for Immutable Records

Blockchain is slowly but surely being adopted in the accounting domain. It has the potential to provide tamper-proof audit trails and secure decentralized record management solutions. For organizations that value chain of custody and data integrity above everything else, block chain-based solutions can provide a level of verifiability that is impossible with conventional databases.

Biometric Authentication

Fingerprint readers, facial recognition systems, and behavioural biometrics have become the norm for access control to sensitive financial systems. This is because they are extremely difficult to breach from a distance compared to conventional passwords.

Cyber Insurance

Cyber insurance has become from a niche product to almost a necessity. It covers the cost of response to cyber attacks, legal fees, client notifications, and fines from regulatory agencies, and even losses from business interruptions. In fact, the median ransomware payment worldwide is now $115,000 (DBIR 2025), and the case for cyber insurance is quite obvious—especially for organizations with small budgets for IT.