A cyber attack by an international criminal gang saw Lloyds Banking Group customers temporarily unable to access their accounts online.
The Financial Times reports several high street banks were hit by the denial of service attack earlier this month, although only Lloyds customers experienced problems.
Denial of service attacks see a website swamped with traffic in a bid to disable it. Customers within the Lloyds group, including Halifax and Bank of Scotland, could not send payments or check their balance online, though no customers suffered a financial loss.
TSB, previously part of Lloyds, was also affected as it still uses the Lloyds technology platform.
The National Cyber Security Centre is investigating a similar attack against Tesco Bank.
The NCSC says: “The more information a company shares in a timely manner, the better we are able to support them and prevent others falling victim. But companies ultimately hold responsibility for their cyber security risks – and they should invest appropriately to ensure their networks are secure.”
Lloyds declined to comment.