The Internal Revenue Service issued an alert Tuesday to payroll and human resources professionals to beware of an emerging phishing email scheme that purports to come from company executives and requests personal information on employees.

The IRS said it has learned this scheme—part of the surge in phishing emails seen this year—already has claimed several victims as payroll and human resources offices mistakenly email payroll data, including Forms W-2 that contain Social Security numbers and other personally identifiable information, to cybercriminals posing as company executives.

“This is a new twist on an old scheme using the cover of the tax season and W-2 filings to try tricking people into sharing personal data,” said IRS Commissioner John Koskinen in a statement. “Now the criminals are focusing their schemes on company payroll departments. If your CEO appears to be emailing you for a list of company employees, check it out before you respond. Everyone has a responsibility to remain diligent about confirming the identity of people requesting personal information about employees.”

IRS Criminal Investigation already is reviewing several cases in which people have been tricked into sharing SSNs with what turned out to be cybercriminals. Criminals using personal information stolen elsewhere seek to monetize data, including by filing fraudulent tax returns for refunds.

This phishing variation is known as a “spoofing” email. It will contain, for example, the actual name of the company chief executive officer. In this variation, the “CEO” sends an email to a company payroll office employee and requests a list of employees and information including SSNs.

The following are some of the details contained in the e-mails:

• Kindly send me the individual 2015 W-2 (PDF) and earnings summary of all W-2 of our company staff for a quick review

• Can you send me the updated list of employees with full details (Name, Social Security Number, Date of Birth, Home Address, Salary) as at 2/2/2016.

• I want you to send me the list of W-2 copy of employees wage and tax statement for 2015, I need them in PDF file type, you can send it as an attachment. Kindly prepare the lists and email them to me asap.

Among the companies that were scammed was the social media mobile app developer Snapchat. “We’re a company that takes privacy and security seriously,” the company said in an apology to its employees Friday. “So it’s with real remorse–and embarrassment–that one of our employees fell for a phishing scam and revealed some payroll information about our employees. The good news is that our servers were not breached, and our users’ data was totally unaffected by this. The bad news is that a number of our employees have now had their identity compromised. And for that, we’re just impossibly sorry.”

Snapchat said that last Friday its payroll department was targeted by an email phishing scam in which a scammer impersonated the company’s CEO and asked for employee payroll information.

“Unfortunately, the phishing email wasn’t recognized for what it was–a scam–and payroll information about some current and former employees was disclosed externally,” said the company. “To be perfectly clear though: None of our internal systems were breached, and no user information was accessed.”

The IRS noted that it recently renewed a wider consumer alert for e-mail schemes after seeing an approximate 400 percent surge in phishing and malware incidents so far this tax season and other reports of scams targeting others in a wider tax community.

The emails are designed to trick taxpayers into thinking these are official communications from the IRS or others in the tax industry, including tax software companies. The phishing schemes can ask taxpayers about a wide range of topics. E-mails can seek information related to refunds, filing status, confirming personal information, ordering transcripts and verifying PIN information.

The IRS, state tax agencies and tax industry have joined together in a public awareness campaign – Taxes. Security. Together. – to encourage taxpayers and tax professionals to do more to protect personal, financial and tax data. See IRS.gov/taxessecuritytogether or Publication 4524 for additional steps.