The warning comes after the first half of 2012 saw reported cases of so-called “card not present” fraud were estimated to have cost retailers and shoppers more than €8m.
Last year saw a 25% growth in credit card fraud.
Particularly prevalent are cases where numbers are stolen, sold to other criminals, and used to buy goods online or by phone, which are then sold for profit.
To scam retailers, criminals first need stolen credit card numbers, which they obtain by getting unwitting consumers to install viruses on their computers or give details to fake websites.
Experts say antivirus software and exercising as much caution online as off, minimises risk, while gardaí say consumers can also help by not buying suspected stolen goods.
Gardaí have also said that retailers can protect customers and themselves by using secure online systems.