Thousands of TalkTalk and Post Office customers have had their internet access cut by a cyber attack.
Certain types of broadband routers used by both the Post Office and TalkTalk were targeted in the attack - damaging people's internet connections.
The attack used a piece of malware known as the Mirai worm, which is spread via compromised computers and works by taking control of devices running the Linux operating system and using them to knock services offline.
TalkTalk acknowledged that a "small number" of customer routers had been affected.
The company said it had deployed "additional network-level controls to further protect our customers".
Earlier, a spokeswoman for the Post Office said the issue had begun for their customers on Sunday but that no personal data from users was at risk.
"Post Office can confirm that on November 27 a third party disrupted the services of its broadband customers, which impacted certain types of routers," they said in a statement.
"Although this did result in service problems we would like to reassure customers that no personal data or devices have been compromised.
"We have identified the source of the problem and implemented a resolution which is currently being rolled out to all customers".
It follows news from Germany's Deutsche Telekom earlier this week that up to 900,000 of its customer had lost their internet connection as part of the same incident.
No-one has yet claimed responsibility for the attack.
A similar attack on the US-based Dyn web domain provider in October knocked a host of prominent websites offline, including Spotify, Twitter and Reddit.