SAS applications will be used to look for suspicious transactions or patterns of behaviour in the bank's current account, personal loan and mortgage businesses.
Paul Devlin, head of Scottish and regional operations at SAS, said the bank would roll out new tools from SAS as and when it perceives the need to do so. "We have seen evidence that fraudsters get used to a company's improved security and move on. And we have also seen them come back again," he said.
SAS software detects fraud including instances of card cloning at ATMs and people lying about their income on mortgage applications, said Devlin.
Alliance & Leicester, like other banks, is increasingly concerned about the increase in phishing attacks - where fraudsters entice a bank's customers to leave their passwords and account details on fake websites.
Although the losses from attacks against banks including NatWest, Lloyds TSB and Barclays have been relatively small, concern is growing that more sophisticated phishing attacks in the future could cause significant losses.