Accounting Firm Cybersecurity Checklist

Why accounting firms are specifically targeted

Attackers target accounting firms because a single successful compromise can expose the financial data of dozens or hundreds of clients at once, and because firms regularly send and receive banking details, making invoice fraud and business email compromise attempts blend in with normal daily communication. This concentration of valuable data and routine financial correspondence is exactly what makes phishing and payment fraud attempts against firms so effective.

Identity and access controls

• Multi-factor authentication enforced on every account, including partners, without exception
• Role-based access to client folders and financial systems, so staff only see the clients they actually work with
• Prompt deprovisioning of accounts for departed staff and expired contractors
• Conditional access policies restricting sign-ins to managed devices where practical

Email and payment fraud defenses

1. Deploy advanced anti-phishing filtering, such as Defender for Office 365, tuned specifically for invoice and payment fraud patterns
2. Require verbal confirmation through a known phone number for any request to change banking or wire instructions, regardless of how legitimate the email looks
3. Tag external emails clearly so staff can spot messages impersonating clients or known contacts
4. Train staff specifically on the tax-season spike in phishing volume, covered in our tax season IT readiness guide

Data protection for client financial records

• Encrypt sensitive client data both at rest and in transit
• Use secure, access-controlled methods for client document exchange rather than unencrypted email attachments, as detailed in our secure client document exchange guide
• Apply a tested 3-2-1 backup strategy to accounting software data and general firm files alike
• Log and periodically review who has accessed sensitive client folders

Endpoint and network protection

Every workstation and server handling client data should run current endpoint protection, receive security patches promptly, and sit behind a properly configured firewall. This applies just as much to the servers and workstations running QuickBooks or Sage 50, covered in our guides to QuickBooks running slow and Sage 50 network performance, since a poorly secured accounting workstation is as much a risk as an unprotected email account.

Testing the plan, not just having one

A written security policy that has never been tested provides limited real protection. Firms should periodically run phishing simulation exercises, test backup restores, and review whether access permissions still match current staff roles. This ongoing review is part of what our cybersecurity services provide for accounting firms, rather than a one-time setup that is never revisited.

Regulatory and professional context

Ontario accounting firms handling personal financial information should be aware of their obligations under provincial privacy expectations and any professional body requirements around client data protection, and should treat cybersecurity as a professional responsibility rather than purely an IT concern. The Canadian Centre for Cyber Security publishes practical, Canada-specific guidance that applies directly to firms of this size.

Sources and further reading

• Canadian Centre for Cyber Security: Phishing guidance

Frequently asked questions