By Simon Zekaria

 

LONDON--TalkTalk Telecom Group PLC (TALK.LN) said on Friday that there has been a "significant and sustained" cyberattack on the group's website, resulting in the launch of a criminal investigation by the British police.

The British telecom operator warned there is a chance that some of its 4 million customers' data has been stolen, including names, addresses and bank details. The breach happened on Wednesday and the criminal inquiry began the day after. The company said investigations are continuing.

TalkTalk said it is working with cybercrime specialists and London's Metropolitan Police to establish what happened and the extent of the theft of any information.

"We take any threat to the security of our customers' data extremely seriously and we are taking all the necessary steps to understand what has happened here," said Chief Executive Dido Harding.

In a letter to customers, the company said: "Unfortunately cyber criminals are becoming increasingly sophisticated and attacks against companies which do business online are becoming more frequent."

It said it has contacted major banks, which will be looking out for any suspicious activity on customers' accounts.

TalkTalk faces off with larger rivals like Vodafone Group PLC (VOD.LN), Sky PLC (SKY.LN), BT Group PLC (BT.A.LN) and Hutchison Whampoa Ltd.'s Three in the U.K. market. TalkTalk shares closed Thursday at 269 pence, valuing the company at 2.57 billion pounds ($3.96 billion).

Write to Simon Zekaria at simon.zekaria@wsj.com

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(END) Dow Jones Newswires

October 23, 2015 03:20 ET (07:20 GMT)

Copyright (c) 2015 Dow Jones & Company, Inc.
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