A warning is going out to consumers ahead of a spending spree on Black Friday and Cyber Monday.
FraudSMART and gardaí say over €4 billion is expected to be spent online with payment cards during November and December.
They are alerting people to the risks of fraud when buying from sites.
Around three quarters of all card fraud happens online.
"One of the most important messages that FraudSMART and the gardaí can get across to consumers for Black Friday and Cyber Monday is that when they are shopping online they only use secure websites," said Fraudsmart Head of Fraud Prevention, Olivia Buckley.
"Secure websites means that you should look out for https - which is 's' for security - and a padlock symbol.
"These are the only sites on which you should make purchases."
Consumers are advised not to use public Wi-Fi when making payments.
Ms Buckley also advises against clicking on pop-up adverts.
"What we're saying to consumers is: if you see an offer that is advertised, don't click on the ad but rather insert the address of that particular company into your browser and search it independently.
"There is a chance that there are fraudulent ads being advertised online and if you click on them you may be brought to a fraudulent website."