Cyber criminals are targeting people in more sophisticated ways all the time, according to Gardaí.

The number of suspicious transactions has doubled over the last five years - with businesses increasingly being targeted.

Speaking at a conference on online crime and money-laundering this morning, the head of the Garda National Economic Crime Bureau, Detective Chief Superintendent Patrick Lordan said the scams are becoming harder for people to spot.

"Whether you are a builder, whether you are a farmer, whether you are a businessman or a banker - they all look like convincing emails that you would get in from your supplier or clients," he said.

"They will  ask you to change bank account details in a lot of cases.

"Once you change those bank account details and the next invoice comes in from that supplier or client - it goes to the wrong account.

"Before you realise it, the money that you sent to your supplier has gone to a criminal's account."

He said criminals often use student bank accounts and even "a deceased person's bank account that they may have come across on their travels."

Supt Lordan said businesses should "never trust an email" and warned that the best thing to do when asked to update details is pick up the phone and talk to your client directly.

"They are getting very good," he said.

"They normally do it when the CEO or your head of finance is away on holidays or away at a meeting.

"They are watching that.

"They are continuously watching - it is their full-time job."

He said the scams often work in the opposite direction with criminals attempting to order products and charge them to legitimate customer accounts.