All of the sites were down on Saturday afternoon.

The division also provides services to iD Mobile, TalkTalk Mobile, Talk Mobile, and to some Carphone Warehouse customers.

Millions of customers who bought mobile phone handsets and contracts through the Carphone Warehouse may have had their personal details leaked after a cyber-attack.

A spokesbeing told us, when quizzed, that the firm wanted to be sure of the number of people affected by the “sophisticated cyber-attack” before notifying customers about the data breach.

The company said it has now implemented additional I.T. measures to prevent such attacks in the future, and that it has also recruited a cyber security firm to investigate how the breach took place.

If you’re wondering exactly what these major hacks mean for consumers, it’s hard to quantify – the cybercriminals could use your date of birth and address information to guess one of your online passwords or answer the security questions to reset it, for example.

Shares in Carphone Warehouse fell two percent this morning as the UK’s Information Commissioner’s Office (ICO) begins “making enquiries” into how the data breach happened and what can be done about it.

Up to 2.2 million customers may be affected. The retailer also vows to close the security hole that hackers were able to infiltrate and further shore up its defenses against future attacks. This move is being criticized by many consumer groups as according to them many customers may not read the email over the weekend and the company should have sent compromised customers repeated text messages to make them aware.

Last month Dixons Carphone reported a 20.6% jump in pre-tax profit to £381m in its maiden full year results since the merger between Dixons Retail and Carphone Warehouse. He tweeted: “This is the #Infosec department at #carphonewarehouse – sorry we can’t take your call right now – all of our agents are busy just now…”

In a statement Carphone Warehouse urged customers to check their online accounts and bank statement for any suspicious activity. It seems that Carphone Warehouse has been sending out letters to potential victims, since the hack was first discovered on August 5th.