Thousands of TalkTalk and Post Office customers have had their internet access cut by an attack targeting certain types of internet routers. A spokeswoman for the Post Office told that the problem began on Sunday and had affected about 100,000 of its customers.

TalkTalk also confirmed that some of its customers had been affected, and it was working on a fix. It is not yet known who is responsible for the attack. Earlier in the week, Germany's Deutsche Telekom revealed that up to 900,000 of its customers had lost their internet connection as a result of the attack. It involves the use of a modified form of the Mirai worm.

UK phone and broadband provider TalkTalk may have once again left its customers exposed to hackers. TalkTalk warned its customers that attackers could have gained access to their names, addresses, credit card and bank details, dates of birth, phone numbers, email addresses and TalkTalk account information.

"Not all of the data was encrypted," the company acknowledged, meaning there would be no trouble reading it. However, the company is not certain any data was actually accessed from the attack, TalkTalk said. TalkTalk doesn't yet know who perpetrated the hack but has received a ransom demand from a group purporting to be behind it.