RBS and NatWest are first British banks to use technology.
A new online security technology called Rapport will offer greater protection for consumers' banking and credit card details, according to NatWest and RBS.
The two banks have become the first in the UK to implement the new software, which was developed by Trusteer.
Customers at the institutions are able to download Rapport for free from the respective banks' websites.
The software then offers additional security on top of firewalls and anti-virus packages.
This includes a warning if there is a risk of a phishing attack, a preventative system to stop Trojans stealing details and a protection system for communications between client and bank.
"Rapport is fast to download and easy to install, but most importantly it allows us to quickly and effectively react to emerging threats," said Gavin Coull, e-Crime prevention manager at RBS Group.
"It also enhances the effectiveness of our existing card reader security."
More than 500,000 RBS and NatWest customers have now downloaded Rapport, he added.
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