Security measures in place by some high street banks for their online accounts could be leaving customers susceptible to banking fraud, according to Which? Computing. The consumer group's latest survey found that online banking fraud doubled in 2008 to £52.5m. The weakest visible security systems are said to be at Abbey and Halifax, while Alliance & Leicester and HSBC's measures were labelled as 'average'. The survey said that Halifax's log-in procedure was the least secure, as customers are more vulnerable to having information stolen by a keylogger criminal. Software is used to monitor every key stroke being typed into a keyboard, and is thought to be the reason for online banking fraud doubling during 2008. Halifax, Abbey, HSBC and Alliance & Leicester have also faced criticism for not automatically logging customers out of their accounts when they leave the website, as their account details could be accessed. The banks have said that hidden security measures in place were more important when protecting customers. Sarah Kidner, editor of Which? Computing, said: 'There are surprisingly big differences between big banks' visible online security systems. The banks may say it's the hidden security measures that count, but to have real confidence in an online account, customers need to see security in place.'