A Nigerian student living in the United States, Amechi Amuegbunam, has been sentenced to 46 months in prison for perpetrating fraud to the tune of $3.7m.

Amuegbunam, 30, was also ordered to pay $615, 555.12 in restitution for his role in a sophisticated email phishing scam otherwise known as Business Email Compromise that caused $3.7m loss to US companies.

The convict and other individuals were said to have between November 2013 and August 2015 sent fraudulent emails to companies in the Northern District of Texas and elsewhere containing misrepresentations that caused the companies to wire transfer funds as instructed on a PDF document that was attached to the email.

He was arrested in Baltimore in August 2015 and charged with scamming 17 North Texas companies out of more than $600,000 using the technique.

Amuegbunam was accused of sending emails that looked like forwarded messages from top company executives to employees who had the authority to wire money.

Amuegbunam tricked the employees into wiring him money by transposing a couple of letters in the actual company email, authorities said.

The Dallas investigation began in 2013 when two North Texas companies reported falling victim to the scheme, each losing about $100,000, according to the complaint.

In the case of Luminant Corp., an electric utility company in Dallas, an employee with the authority to wire money received an email from someone who appeared to be a company executive, the complaint said.

But the email domain name had two letters transposed. For example, someone created the email with a domain name of lumniant.com <http://lumniant.com>.

The duped employee wired $98,550 to a bank account outside Texas.

The Federal Bureau of Investigation subpoenaed information about the email account and learned it was created by someone named Colvis Amue, the complaint said.

In another case involving Amuegbunam, a company accountant received an email from her chief executive, who was on vacation outside the country. He asked her to transfer money for a “time-sensitive acquisition” before the day’s end, according to the FBI.

The executive said a lawyer would contact her with more information.

The accountant said such requests were not unusual.

The lawyer sent her an email with her CEO’s signature on a letter of authorisation with the company’s seal that was attached. The email gave her instructions to wire more than $737,000 to a bank in China.

The accountant learned about the scam when the CEO called the next day, saying he knew nothing about the wire transfer request.

The FBI subsequently issued an alert about the new cyber attack it called the “Business Email Compromise.” The FBI said it was a “growing fraud that is more sophisticated than any similar scam the FBI has seen before.”

FBI investigations in conjunction with the Economic and Financial Crimes Commission in Nigeria, led to the arrest of the convict.

Following the conviction of the Nigerian, the FBI commended the EFCC, for its dedication and support in bringing Amuegbunam to justice, the EFCC spokesman, Mr. Wilson Uwujaren, said in a statement.