Insider Threat in Finance Teams: Warning Signs and Practical Controls

An insider threat in a finance team is the risk that someone with legitimate access, such as an employee, contractor or former colleague, causes harm through carelessness, a mistake or deliberate wrongdoing. The warning signs are usually behavioural and procedural rather than technical, and the most effective controls are the familiar ones: segregation of duties, timely access changes when people join, move or leave, and a safe way to raise concerns.

What counts as an insider threat

The US Cybersecurity and Infrastructure Security Agency (CISA) describes insider threat as the risk that an insider misuses authorised access, knowingly or not, to cause harm. It separates unintentional threats, which cover negligence (knowing the rules but ignoring them) and accidents (such as sending a file to the wrong person), from intentional ones, where someone deliberately causes harm for gain or out of a grievance. It also recognises collusion with outsiders and threats from contractors and vendors (CISA).

The UK's National Protective Security Authority (NPSA) uses a similar definition: an insider is anyone who has, or previously had, sanctioned access to an organisation's people, information, technology or premises (NPSA, 2023). That "previously had" matters for finance teams, because leavers with live access are a recurring weak point.

Careless insiders: the everyday risk

Most insider incidents are not crimes. Verizon's 2025 Data Breach Investigations Report found that the human element was involved in around 60% of breaches, and that misdelivery, sending information to the wrong recipient, remained the leading type of error (Verizon, 2025).

In finance, careless insider risk looks like:

• Emailing a payroll or customer file to the wrong address.
• Exporting ledgers to a personal device or unapproved cloud folder to work from home.
• Sharing logins for the banking portal "to save time".
• Approving a supplier bank-detail change without a call-back check, because the request looked routine.

That last example is where carelessness meets criminal targeting. Our guide to phishing, social engineering and business email compromise explains how outsiders exploit well-meaning staff.

Malicious insiders: payment fraud and data theft

The Association of Certified Fraud Examiners (ACFE) studied 2,402 occupational fraud cases from 143 countries and territories for its 2026 Report to the Nations. The median loss per case was $104,000, a typical fraud ran for 12 months before detection, and organisations were estimated to lose 5% of revenue to fraud each year (ACFE, 2026). Accounting and operations were the two departments with the most cases, at 13% each, and accounting cases had a median loss of $164,000 (ACFE, 2026).

Among asset misappropriation schemes, billing schemes were among the most common at 21% of cases, while cheque and payment tampering had the highest median loss at $114,000 (ACFE, 2026). Typical finance schemes include:

• Fictitious or shell suppliers paid through the normal purchase-to-pay process.
• Altering payee bank details on a genuine invoice.
• Payroll "ghost employees" or inflated expense claims.
• Copying customer or employee data before leaving to join a competitor.

Warning signs to notice

Behavioural red flags are common. In the ACFE's 2026 study, 84% of fraudsters showed at least one, most often living beyond their means (39%) or financial difficulties (29%). Others included an unusually close relationship with a vendor or customer (17%) and control issues or unwillingness to share duties (12%). Importantly, 16% of frauds showed no red flags at all (ACFE, 2026).

Process and data warning signs in a finance team can include:

• Someone who never takes leave or resists handing over their tasks.
• Repeated "urgent" manual payments outside the normal run.
• Supplier records changed shortly before a payment, then changed back.
• Reconciliations that are always late, or always done by the same person with no review.
• Large downloads or reports run outside normal hours or job role.

A single sign proves nothing. The aim is to notice patterns and let the right people look, not to accuse colleagues.

Practical controls that work

Segregation of duties

No one person should be able to create a supplier, approve an invoice and release the payment. In the ACFE's 2026 data, a lack of internal controls was the primary weakness in 33% of cases, an override of existing controls in 19% and a lack of management review in 18% (ACFE, 2026). In small teams where full separation is impractical, use compensating controls such as independent review of payment runs and bank-detail changes.

Joiners, movers and leavers

• Joiners: give access based on role, not on what the previous post-holder had.
• Movers: remove old access when someone changes role. Permissions that pile up over time undermine segregation of duties.
• Leavers: revoke access on the last day, including banking portals, shared mailboxes and cloud tools.

Regular access reviews help catch what slips through. Our guide to cybersecurity policies for finance departments covers how to write these processes down.

Monitoring and mandatory checks

Surprise audits, management review and proactive data analysis were each associated with lower losses and faster detection in the ACFE's study (ACFE, 2026). Simple steps, such as exception reports on bank-detail changes and duplicate payments, are within reach of most finance teams.

How to raise a concern

Tips were how 43% of frauds were detected, and 55% of those tips came from employees (ACFE, 2026). Make reporting easy and safe:

• Know your organisation's reporting channel and who receives reports.
• Write down what you observed, with dates, but do not investigate or confront the person yourself.
• In Ireland, the Protected Disclosures (Amendment) Act 2022 has applied since 1 January 2023, and private employers with 50 or more employees must have formal internal reporting channels (Office of the Protected Disclosures Commissioner, 2023).
• In the UK, reporting a criminal offence such as fraud can be a protected disclosure if it is in the public interest; personal grievances generally are not covered (GOV.UK).

This section is general information, not legal advice. Take advice on your specific situation if needed.

Frequently asked questions

Is insider threat mainly about dishonest employees?

No. CISA and NPSA both include accidental and negligent actions. In finance, mistakes such as misdirected emails or skipped verification checks are far more common than fraud.

How can a small finance team segregate duties?

Split the key steps between at least two people where you can, and where you cannot, add independent review of payment runs, bank-detail changes and reconciliations, for example by a manager or external accountant.

Should I report a hunch?

Report what you observed, not your conclusion. Facts such as "supplier bank details changed twice this week without a ticket" help investigators far more than suspicions about a person.

Insider risk is managed by everyday habits and fair, well-designed controls. To keep your skills current, explore Learnsignal's finance and compliance CPD courses.