Vendor Email Was Hacked and We Paid the Wrong Account: Who Is Responsible?

When your vendor’s email is hacked and you pay a fraudulent invoice, the immediate financial loss is only the beginning. The question of who is legally responsible for that loss—you or your vendor—is complex and stressful. There is no simple answer; liability often depends on the specific facts of the case, the governing laws in your jurisdiction, and the terms of your contracts.

Generally, the resolution comes down to which party was in the best position to prevent the fraud and whose negligence most directly allowed it to happen. Courts have examined these disputes through the lens of the "impostor rule" under the Uniform Commercial Code (UCC), but its application varies by state. The outcome often hinges on a detailed analysis of each party's security controls and actions leading up to the fraudulent payment.

If you just sent a fraudulent wire transfer due to a suspected vendor email compromise, contact our 24/7 incident response team immediately at business email compromise.

This article will walk you through the factors that determine responsibility, the immediate steps to take after discovering the fraud, and when to bring in professional help. We will focus strictly on the scenario where your vendor's email system was the source of the compromise, leading to you making an improper payment.

How is liability determined when a vendor's email is hacked?

Determining who bears the financial loss involves a factual investigation into the "reasonableness" of each party's security practices and payment verification procedures. Attorneys will scrutinize the "chain of events" that led to the fraudulent payment. While the specifics are highly fact-dependent, the analysis will revolve around a few key questions.

• Whose system was compromised? In this scenario, the initial breach occurred on the vendor's side. This fact often puts the initial burden on the vendor to demonstrate they took reasonable steps to secure their systems.
• Was there negligence? The core of the legal argument will likely be about negligence. Did the vendor fail to implement basic security measures like multi-factor authentication (MFA), leading to the account takeover? Conversely, did your team fail to follow established payment verification protocols? Did you approve a change in banking details without a phone call or other out-of-band confirmation?
• What do your contracts say? Your contracts with the vendor may contain clauses that assign liability for fraud, data breaches, or require specific security standards. These contractual obligations can be decisive.
• Who was in the best position to prevent the fraud? A court may look at which party had the last, best chance to stop the fraudulent transaction. Even if the vendor was initially hacked, if your accounts payable team ignored multiple warning signs and bypassed your own internal controls, you might share or even bear the full responsibility.

Ultimately, these disputes are often resolved through negotiation between the parties, their banks, and their insurance companies. In some cases, they can lead to costly litigation.

What are the first steps to take after paying a fraudulent invoice?

Time is critical. The moments after you discover a fraudulent payment can determine whether the funds are recoverable. You must act immediately and methodically.

1. Call Your Bank Immediately. This is the most important first step. Contact your bank's fraud department by phone. Inform them that the wire transfer or ACH payment was fraudulent. If notified quickly enough—sometimes within hours—they may be able to halt or reverse the transaction. Initiate a SWIFT recall for wire transfers or an ACH reversal. The sooner you act, the higher the chance of success.

2. Notify the Vendor. Inform your vendor—using a known, trusted phone number—that their email account is likely compromised and has been used to defraud you. This is crucial for containment. They need to secure their account to prevent the attacker from victimizing other customers. Do not use email to communicate this, as the attacker may still control the account.

3. Preserve Evidence. Do not delete anything. Preserve all relevant records: the fraudulent invoices, the email chains with the attacker (even if they appear to be from the vendor), payment confirmations, and any internal communications about the payment. This evidence is vital for the investigation, your insurance claim, and any legal proceedings.

4. Report to Law Enforcement. File a report with the FBI's Internet Crime Complaint Center (IC3) at ic3.gov. The FBI's Recovery Asset Team (RAT) can, in some cases, work with the destination bank to freeze the funds. This process is most effective when initiated within 24-48 hours of the transaction. You should also report the crime to your local FBI field office.

5. Launch an Internal Investigation. You must determine how this happened and if the attacker has compromised your own systems. Even though the fraud originated from a vendor's environment, the attacker may have also targeted your organization. Review your own email logs for suspicious activity. A professional incident response firm can help you conduct a thorough investigation to confirm your systems are secure.

When should we get outside incident response help?

While your internal IT team is a critical part of the response, an external incident response firm is warranted when the financial, legal, and operational stakes are high. Consider bringing in a firm like Lyra Recovery if:

• The financial loss is significant. If the fraudulent payment puts your business at financial risk, you need experts who specialize in fund recovery and crisis management.
• You need to prove your own systems are secure. To effectively negotiate with your vendor, you will need to definitively prove that the breach did not originate on your end. A third-party investigation provides an independent, authoritative report to support your position.
• You suspect the attacker may have access to your email. If there is any chance the attacker also compromised one of your accounts, you need a rapid and thorough investigation to eject the threat actor and secure your environment. Hackers often remain inside compromised Microsoft 365 accounts for weeks or months.
• You need to navigate insurance, legal, and regulatory obligations. A seasoned incident response team can provide the technical documentation required for cyber insurance claims and legal proceedings.
• Your team is overwhelmed. A major fraud event is an "all hands on deck" crisis. An external firm allows your team to focus on running the business while experts manage the complexities of the investigation and recovery.

Frequently Asked Questions

Can't we just blame the vendor since their email was hacked?

While the vendor's compromised email was a key factor, it doesn't automatically absolve you of responsibility. If your organization did not follow reasonable "know your customer" or payment verification procedures, you may be found partially or fully liable for the loss. The concept of contributory negligence is often applied.

Will cyber insurance cover the loss?

It depends on your policy. Some cyber insurance policies have specific coverage for social engineering fraud or business email compromise. Other policies, like crime or fidelity policies, may apply. However, coverage often depends on demonstrating that you followed your own internal controls. Be prepared for a detailed claims process. Our guide on cyber insurance requirements after a breach provides more detail.

What if we both had weak security?

This is a common scenario. If both parties failed to use multi-factor authentication and had poor payment verification processes, liability may be split, or the loss may lie where it fell. These situations often result in negotiated settlements or protracted legal disputes.

How can we prevent this from happening again?

Preventing vendor email compromise requires a multi-layered approach.

• Implement a strict payment verification process. All requests to change banking information must be verified via an out-of-band method, such as a phone call to a known contact at the vendor.
• Conduct security awareness training. Train your employees, especially in finance and accounts payable, to recognize the signs of phishing and social engineering.
• Assess your vendors' security. Don't be afraid to ask your critical vendors about their own security practices, such as their use of MFA.
• Improve your own email security. Secure your own email environment with MFA, Conditional Access policies, and robust threat detection. Read our business email compromise recovery guide for a comprehensive overview of defensive measures.

Dealing with the fallout of a vendor email compromise is a challenging situation. The legal and financial questions are complex, and the need for a swift, expert-led technical investigation is paramount. By taking the right steps, you can mitigate the damage and strengthen your defenses against future attacks.

If you have paid a fraudulent invoice after a vendor email hack, your priority must be immediate, decisive action. Lyra Recovery’s incident response team is available 24/7 to help you navigate the crisis, investigate the breach, and engage with financial institutions. Contact us now to begin the recovery process.