A customer database left unsecured online by Virgin Media contained details linking some customers to pornography and explicit websites.
The researchers who first discovered the database told the BBC that it contained more information than Virgin Media suggested.
Such details could be used by cyber-criminals to extort victims.
Virgin Media told the BBC only a small number of customers had these sensitive details in the database.
It said it was in the process of contacting customers again about specific data that may have been stolen.
The telecoms company revealed on Thursday that one of its “marketing databases” containing details of 900 ... Read even more