How should organisations prevent vendor email compromise from bypassing normal approval workflows?

Why This Matters for Security Teams

vendor email compromise is not just a phishing problem. It is an identity-routing problem that exploits trust already built into procurement, finance, and supplier operations. When attackers compromise a supplier mailbox or convincingly impersonate one, they can redirect payments, alter bank details, or change billing destinations without triggering the controls that usually protect internal systems. That is why email thread continuity should never be treated as proof of legitimacy.

This risk becomes more acute as organisations automate approvals and exception handling. A familiar request inside an existing thread can bypass instinctive scrutiny, especially when business urgency, seasonal volume, or executive pressure narrows review windows. NHI Management Group’s research on 52 NHI Breaches Analysis shows how often compromise succeeds by abusing trusted identity relationships rather than defeating perimeter defences. Attackers also increasingly use AI to scale impersonation and social engineering, as reflected in Anthropic's first AI-orchestrated cyber espionage campaign report. In practice, many security teams encounter the damage only after a payment has already left the organisation, rather than through intentional control testing.

How It Works in Practice

The most reliable defence is to treat supplier changes as high-risk identity events, not routine administrative requests. That means requiring out-of-band verification for any request that changes bank accounts, payee details, contact records, or billing instructions. The verifier should use a trusted supplier record, not the email thread itself, and approval authority should be split so the requester and approver cannot be the same person.

Operationally, the control set should include:

• Call-back verification using a previously trusted number from the supplier master record
• Two-person approval for payment destination changes and urgent exceptions
• Documented change windows for vendor master data updates
• Alerting for domain lookalikes, display-name spoofing, and mailbox rule tampering
• Mandatory reconfirmation when a request deviates from normal supplier behaviour

Email security controls help, but they are not sufficient on their own. A strong DMARC posture can reduce direct spoofing, while supplier identity validation should be anchored in a controlled record system and a verified contact path. The broader lesson from The State of Secrets in AppSec is that organisations often overestimate the maturity of their trust controls while underestimating how quickly attackers exploit exposed or abused credentials. This same trust gap appears in procurement workflows when approvals are treated as clerical steps instead of security decisions. Current guidance suggests pairing policy enforcement with finance-system controls so that high-risk changes cannot be completed by email alone. These controls tend to break down when supplier records are poorly maintained, because verifiers then fall back to the compromised mailbox as the default source of truth.

Common Variations and Edge Cases

Tighter approval controls often increase cycle time, so organisations must balance payment speed against fraud resistance. That tradeoff is most visible in shared-service centres, high-volume invoice processing, and seasonal purchasing spikes where staff are tempted to fast-track exceptions.

There is no universal standard for this yet, but best practice is evolving toward risk-based verification. For low-risk vendor updates, a documented workflow may be enough. For bank-detail changes, new beneficiaries, or requests tied to urgency, the threshold should be much higher and ideally require live human confirmation from a pre-verified channel. Organisations should also watch for edge cases where a legitimate supplier is themselves compromised, because a trusted relationship can still be weaponised even when the address and branding appear correct.

Security teams should align this process with DeepSeek breach lessons on compromised trust assets: once an attacker controls the identity channel, standard approval workflows may simply accelerate the fraud. In supplier onboarding, invoice disputes, and urgent one-off payments, the control failure usually happens when staff prioritise business continuity over verification discipline.

Related resources from NHI Mgmt Group

• How can organisations reduce the impact of vendor fraud in email workflows?
• How should security teams reduce vendor email compromise risk in finance workflows?
• What do organisations get wrong about reported-email handling?
• Why do rules-based email controls fail against modern phishing and vendor impersonation?