CFOs across the world are being targeted by a scam aimed at tricking them into sending company funds to a group of hackers based in Nigeria, according to cybersecurity firm Agari.

The US firm says it investigated the group after coming under attack itself. “Targets included companies in a very broad range of sectors, from small businesses to the largest multinational corporations,” the company says in a report.

Agari warns attackers are carrying out an increasingly common scam known as a “business email compromise” in which they attempt to pose as a company insider, such as the CEO, requesting a money transfer to an outside account.

The attack reinforces the need to consider cyber security as a board level issue.