Call the cardholder when the expected benefit of certainty outweighs the time cost of the review. Email is often poor for verification because fraudsters can create disposable addresses quickly, and it may be harder to distinguish them from legitimate customers. Use calls selectively, and only when the additional confirmation meaningfully improves the decision.
Why email is often a weak verification channel
Email can support review, but it is a poor proof of control over a cardholder relationship. Disposable addresses, inbox forwarding, and compromised mailboxes make it easy for a fraudster to imitate the expected communication path while staying outside stronger verification. In practice, email is best treated as a low-friction signal, not as a standalone identity check.
This matters because fraud review is a decision under uncertainty. If the channel used to confirm the customer can be copied, rerouted, or monitored by the attacker, then the review outcome can be manipulated without ever exposing that the contact itself is untrustworthy.
- Use email for notification, case updates, or follow-up when the decision is already low risk.
- Do not treat a matching reply thread as proof that the cardholder is the one responding.
- Escalate to a stronger channel when the transaction value, velocity, or pattern would make a false approval expensive.
When a call changes the decision
A call is justified when the extra certainty can change the fraud outcome more than it delays the review. That is usually true when the case sits near the approval threshold, the transaction is unusual for the customer, or the cost of a false positive is high enough that a quick live confirmation is worth the operational time.
Phone contact is not a universal fix. It only helps if the fraud team can reach a reliable number, ask a question that a fraudster is unlikely to answer convincingly, and record the result in a way the reviewer can trust later. If those conditions are missing, a call may add friction without adding real assurance.
- Call when the case is ambiguous and the answer will materially affect approve versus decline.
- Prefer calls for unusual high-value purchases, repeated attempts, or cases with weak digital corroboration.
- Skip the call when the decision is already obvious from stronger evidence or when the delay would create more operational harm than benefit.
Risk and Threat Considerations
The main risk is over-trusting a channel that is easy to imitate. Fraudsters can create email accounts quickly, intercept messages through compromised mailboxes, or exploit weak manual judgment when analysts try to “fill in the gaps” from incomplete evidence. A phone call reduces that risk only when the callback path and the question asked are both strong enough to resist social engineering.
Failure mechanism: The review process accepts a low-assurance signal as if it were proof of customer intent, letting an attacker steer the approval decision through a channel they can control or spoof.
Impact: The team approves fraudulent transactions, misses repeat abuse patterns, and trains itself to trust the wrong signals, which increases losses and weakens future review quality.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CIS Controls v8 and NIST CSF 2.0 set the technical controls, while PCI DSS v4.0 define the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | 6 — Access Control Management | Limits reliance on weak verification paths and supports stronger review gating. |
| Recommendation — Require stronger verification for high-risk approvals and restrict acceptance of low-assurance contact signals. | ||
| NIST CSF 2.0 | PR.AA-01 — Identities and credentials are issued, managed, verified, revoked, and audited | Fraud review depends on verifying that the contact and account signals are trustworthy. |
| DE.AE-02 — Detected events are analyzed to understand attack targets and methods | Fraud review must interpret suspicious communication patterns as part of the threat picture. | |
| Recommendation — Verify and audit customer contact paths before using them as approval evidence. Analyze suspicious contact patterns to distinguish legitimate customers from fraud indicators. | ||
| PCI DSS v4.0 | 8 — Identify users and authenticate access to system components | Cardholder-related decisions benefit from stronger authentication of contact and review evidence. |
| Recommendation — Require stronger authentication and verification before accepting high-risk payment decisions. | ||
Practitioner Guidance
What to prioritise: Use calls for cases where certainty is the scarce resource, not as a default reaction to every suspicious event. The best trigger is not “does this look odd,” but “would one additional confirmation step change the outcome enough to justify the delay?”
What to verify: Confirm that the phone number comes from a trusted record, not from the disputed transaction or a message thread the attacker could influence. A call only improves certainty if the team controls the contact path as well as the conversation.
Decision rule: If the case is low value or already well supported by other evidence, keep it on the faster review path. If the case is high impact and the digital evidence is thin, spend the time on live confirmation rather than trusting email alone.
Practitioner takeaway: The right test is not whether a call is inconvenient, but whether the added certainty is worth more than the review delay and operational cost.
Related resources from NHI Mgmt Group
- How should security teams enforce email information barriers without relying on static DLP alone?
- How should security teams evaluate LLMs for enterprise workloads instead of relying on public benchmarks alone?
- How should security teams prevent business email compromise in finance workflows without relying on awareness training alone?
- How should security teams build intrusion detection for CI/CD environments instead of relying on logs alone?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 20, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
