When Vendor Compromise Becomes Financial Risk

Security teams often use the term Vendor Email Compromise (VEC) to describe attacks where a vendor’s email account is taken over and used to facilitate fraud. Finance teams may refer to the same issue as vendor compromise, vendor fraud, or payment fraud because the business impact is ultimately financial.

While the terminology varies, the risk is the same: attackers exploit trusted vendor relationships to manipulate communications, redirect payments, and steal money. The challenge isn’t what teams call it—it’s stopping compromised vendors from turning trust into financial loss.

VEC is often grouped under the broader category of Business Email Compromise (BEC), but the attacks work differently. Traditional BEC typically relies on impersonation or spoofed emails, while VEC involves a legitimate vendor account that has already been compromised. Because the communication comes from a trusted account, many of the controls organizations use to stop BEC may never be triggered. This means defending against VEC requires a different approach—it should be focused on vendor behavior, payment workflows, and financial risk.

Compromised vendor attacks are effective because they exploit trusted business relationships. Instead of impersonating a vendor, attackers gain access to a legitimate vendor account and operate through real email threads, invoices, and payment workflows. Because the communication appears authentic, these attacks can bypass traditional email security controls and evade manual verification processes, making them difficult to detect before the money is transferred.

Bank account validation answers one question: “Is this a real bank account?” It doesn’t answer the more important one: “Should I send money there?” Trustmi research found that 90% of fraudulent bank accounts used in payment fraud were approved by their banks. In vendor compromise attacks, fraudsters often use legitimate accounts and trusted vendor relationships to redirect payments, allowing fraudulent requests to pass this traditional validation check.

One of the most common signs of vendor compromise is a request to change banking details or payment instructions. While these updates are a normal part of doing business, they’re also one of the most common ways attackers redirect payments. When a trusted vendor suddenly asks for changes to banking information, invoices, contact details, or payment processes, it’s worth taking a closer look.

Not always. While email security is effective at detecting phishing, malware, and spoofed domains, Trustmi research found that 85% of payment fraud attacks begin in email, and they bypass email security. This is because in many vendor compromise attacks, the message comes from a legitimate vendor account and references real business activity. The email may be authentic—the payment request is not.

Trustmi uses Behavioral AI to identify risk across vendor, invoice, payment, and communication workflows. Instead of relying on a single indicator, Trustmi analyzes hundreds of behavioral signals to understand what is normal for a vendor relationship and detect when something changes. By connecting risk signals across email, ERP, AP, banking, and payment systems, Trustmi helps organizations identify compromised vendors and stop fraudulent payments before money moves.