5 Principles to a Strong Cybersecurity Plan for Accounting Firms

Accounting firms are under attack, and having a strong cybersecurity plan has never been more important. With 25% of all cyberattacks targeting the financial services industry and 43% aimed at small and midsize businesses (SMBs), the risks are real and growing. To help your firm prepare for, prevent, and respond to these evolving threats, we’ve outlined five core principles that form the foundation of an effective cybersecurity plan for accounting firms. Drawing on more than 30 years of experience serving professional services firms, we’re confident these insights will help you strengthen your defenses and protect client data.

1. Defense in Depth: Your Multi-Layered Shield

Think of your firm’s security like a medieval fortress that has several layers of defense: first, the moat, then the outer wall, and if you penetrate the courtyard, then the keep. Defense in depth uses the same concept—multiple barriers that work together to protect your clients’ sensitive financial information.

For accounting firms, this layered approach is particularly critical given the variety of access points to your systems. Your defense strategy should include:

• Multi-factor authentication for all client data access, especially during tax season when temporary staff may be onboarded 
• Endpoint protection on every device that touches client files, including partners’ home computers and mobile devices 
• Network segmentation that separates client data from administrative systems 
• Encrypted file storage for tax returns, financial statements, and audit working papers 
• Regular vulnerability assessments of your document management and tax preparation software 

When one security measure fails—and eventually, something will—the other layers continue protecting your firm and your clients’ trust.

For example, most of our clients use ITDR (Identity Threat Detection and Response), which continuously monitors user behavior and flags unusual activity. If credentials are compromised, the system automatically isolates and contains the threat before it can spread. In fact, our ITDR platform stops one to two business email compromise (BEC) attacks every week—often before users even realize there was a risk.

This proactive approach aligns with the trends we explored in our recent blog on AI-driven cyberattacks targeting accounting firms, where we highlighted how emerging AI-based threats are reshaping attack methods and increasing the urgency for intelligent, adaptive defenses.

2. Principle of Least Privilege: Need-to-Know Basis

A marketing intern doesn’t need the same access as a tax partner or a systems administrator. The principle of least privilege ensures staff members can only access the client files and systems necessary for their current assignments.

This principle is fundamental in accounting firms where:

• Seasonal workers require temporary access during busy periods 
• Junior staff should have restricted access to high-value client accounts 
• Administrative personnel need different permissions than audit teams 
• Partner-level access should be protected with additional authentication 

We recommend implementing quarterly access reviews to combat “privilege creep”—the gradual accumulation of unnecessary permissions as staff move between engagements or departments. This regular housekeeping prevents former employees or transferred staff from retaining access to sensitive client information.

3. Separation of Duties: Trust, but Verify

Internal control is a foundational concept in accounting, and the same principle applies to  cybersecurity plan for accounting firms. Critical operations—especially those affecting multiple client accounts or firm-wide systems—should require approval from multiple authorized individuals.

Practical applications for accounting firms include:

• Dual approval for wire transfers and electronic payments above certain thresholds 
• Separate roles for those who can create new user accounts versus those who assign permissions 
• Two-person authorization for bulk changes to client data or mass communications 
• Independent review of system configuration changes and security policy updates 

This separation makes it exponentially harder for a single compromised account or malicious insider to cause widespread damage.

4. Secure by Design: Build Security In, Don’t Bolt It On

Often, firms implement new software or processes first, then try to secure them later. This backward approach leaves gaps that attackers can exploit. Instead, security must be an initial consideration before new technology is purchased and implemented.

When your firm considers new initiatives—whether it’s cloud migration, remote work capabilities, or new client portals—security professionals should be involved from the planning stage. Key considerations include:

• How will client data be protected in transit and at rest? 
• What compliance requirements (SOX, GDPR, state privacy laws) apply? 
• How will you maintain audit trails for regulatory purposes? 
• What happens to client data when engagements end? 

5. Keep It Simple: Security That People Actually Use

The most sophisticated security system fails if your team finds workarounds because it’s too complicated. While protecting sensitive financial data requires robust measures, excessive complexity often backfires.

Consider these accounting firm realities:

• Partners juggling multiple client emergencies won’t tolerate systems that slow them down 
• Tax season’s frantic pace means security measures must be intuitive 
• Remote work requires seamless but secure access 
• Client-facing systems need to be secure without frustrating those you serve 

Strike the right balance by focusing on high-impact, low-friction security measures. For instance, single sign-on with multi-factor authentication provides strong protection while simplifying the user experience. Password managers eliminate the need to remember dozens of complex passwords while improving overall security.

Moving Forward

Together, these five principles form the foundation of a comprehensive cybersecurity plan for accounting firms—one that protects your business, your reputation, and most importantly, your clients’ trust. Remember, cybersecurity isn’t a one-time project but an ongoing commitment. Regular reviews, updates, and employee training are essential to keep your defenses strong as new threats emerge.

Start by assessing your current security posture against these principles. Where are your gaps? Which principle needs the most immediate attention? By methodically applying these fundamentals, you’ll build a security program that’s both robust and sustainable—essential qualities for protecting your accounting firm in an increasingly dangerous digital world.