A huge cyber attack against JPMorgan Chase this summer compromised customer information for about 76 million US households and seven million small businesses, the bank said.

Usernames and passwords of some of Yahoo’s email customers have been stolen and used to gather personal information about people they have recently corresponded with.

The sophistication of a global network of thieves who drained cash machines around the globe of $45m (€35m) in mere hours sent ripples through the security world, not merely for the size of the operation and ease with which it was carried out, but also for the threat that more such thefts may be in store.