Cyber security for accountancy
Cyber security that protects client data and busy season at the same time
Accountancy practices are a high-value target with a thin headcount. Client data is sensitive, email is the workflow, and the ICO and AML supervisors expect competent technology. Good security for a practice tightens the obvious openings without making January harder.
Looking at the bigger picture across IT support, cyber, AI and digital transformation? See the full accountancy technology overview.
Why it matters
Cyber security in accountancy is operational, regulatory and commercial all at once
An accountant's inbox holds the kind of detail a fraudster needs to be convincing: payroll dates, bank changes, director information, year-end timings. Targeted phishing and impersonation of partners and clients are now routine, not exotic.
On top of that, practice software, portals and Microsoft 365 hold years of client documents. A compromised partner mailbox or a misconfigured OneDrive can become an ICO conversation very quickly.
The threat shape
What attacks on accountancy businesses actually look like
BEC and bank-detail fraud
'Our client has changed their bank details' emails are the most common path to a loss. Impersonation of partners is increasingly convincing.
Phishing through tax season urgency
January and year-end create a window where staff are tired and time-pressured. Click rates rise, MFA fatigue follows.
Mailbox compromise and silent forwarding
Attackers stay quiet inside a mailbox for weeks, setting up rules and waiting for the right invoice to land.
OneDrive and SharePoint sprawl
Client folders shared with personal accounts, dormant guests and external links that nobody reviews.
Non-negotiables
What effective cyber security for accountancy looks like in practice
Hardened email and impersonation defence
DMARC, DKIM, SPF, anti-impersonation policies, and a tested response for 'a client's accountant has changed bank details' messages.
MFA and conditional access everywhere
Including admin accounts, including the partners. Phishing-resistant where the role justifies it.
Backups that survive an account compromise
Off-tenant, immutable Microsoft 365 backup, restored regularly. Mailbox compromise is the most likely incident.
Document workflow that ends password-PDF email
A portal or signing flow that gets sensitive client data off the back of email attachments.
What good looks like
A partner who has secured accountancy firms before saves you the first 12 months of learning
A practice-aware security partner closes the obvious openings first: email, identity, and the most exposed mailboxes. They'll back Microsoft 365 properly, tidy the worst of the OneDrive sharing, and brief the team on what BEC actually looks like.
Around busy season they're more present, not less. AML, ICO and Cyber Essentials evidence are sorted in the quieter months so January doesn't include a breach call.
Outcomes you should expect
- Email tightened against BEC and impersonation without breaking workflow
- Microsoft 365 backed up and tested, not just configured
- AML and ICO-relevant evidence kept current
- Busy season survived without a security P1
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