NatWest and RBS have been crowned the UK's most secure online banking providers by consumer group Which?, with Santander ranked bottom of the pile.
With online banking fraud losses hitting £40 million last year, Which? put the Internet services of 10 providers through their paces.
NatWest/RBS scored 76% thanks to features such as the requirement to use card readers when carrying out higher risk tasks like transferring money to a new payee or changing the password.
NatWest also locked the testers out of their accounts for 10 minutes when they tried to log on from two different IP addresses at once - a measure that helps deter fraudsters from accessing accounts when the customer is already using the service.
The research shows that most banks offer a similar level of security to online customers: The Co-op and HSBC both score 72%, Barclays 71%, Norwich and Peterborough 70%, Lloyds TSB and Nationwide 69%, Smile 68% and Halifax 67%.
However, Santander managed just 47%, falling down compared with other banks in terms of how it dealt with security for logging out. The Spanish-owned bank told Which? that it has taken measures to beef up the process but has failed to allay its concerns.
In contrast, First Direct initially scored just 46% thanks to poor security when setting up a new payee but managed to placate Which? by tweaking its system.