Former HSBC bank worker Paul Walsh has been jailed for two years after stealing more than £32,000 from a victim of the London suicide bomb attack on 7 July 2005.
In a classic case of insider fraud, Walsh was able to get around security measures to extend the credit limit of bombing victim Anthony Fatayi-Williams in 2006, according to reports.
Walsh raided the account 90 times with a dummy card used only by bank employees, while working in the bank's Market Hill branch in Cambridge.
The fraudster also stole £750 from a woman whose account was frozen after she was sectioned under the Mental Health Act.
Walsh was arrested and sacked when the scam was exposed in July 2007.
Cambridge Crown Court Judge Jonathan Haworth said Walsh had been a highly trusted employee of the bank.
"You are guilty of gross breach of that trust," he said.
An HSBC spokesman said the bank has worked closely with the police to ensure a successful prosecution.
Internal fraud made up more than a quarter of the £1.19bn in losses recorded in UK court cases in 2008, according to KPMG's annual Forensic Fraud Barometer.
The biggest culprits were managers, who accounted for 56% of internal fraud. They are in a better position to abuse their position of trust, the report said.