A 16-year-old boy from London has been arrested in connection with the investigation into alleged data theft from TalkTalk.
Police confirmed officers carried out a search at a residential property in Liverpool in connection with the cyber attack.
It comes after a boy of 15 was held in Northern Ireland on suspicion of offences under the Computer Misuse Act over the same data breach.
The telecommunications company shut down its site following what it described as a "significant and sustained" attack in which customer details may have been stolen.
TalkTalk says the data hacked "is significantly less than originally suspected" with fewer than 1.2m customer email addresses, names and phone numbers accessed along with fewer than 21,000 unique bank account numbers and sort codes.