Deutsche Telekom said that it could have been the victim of a hacking attack after around 900,000 broadband customers started seeing coverage outages starting yesterday.
At no time was Deutsche Telekom's network infected, according to the company, and filter measures have been implemented to protect the network.
The head of Deutsche Telekom's IT security says the attack seems to be tied with an attempt to infect routers of customers that has a new version of the Mirai software.
For example, it was found that web-enabled home security cameras and DVRs played a significant part in a major denial-of-service attack last month that took down popular services such as Twitter, Spotify, Netflix, CNN, and Airbnb, among others.
Deutsche Telekom said in a statement that the rest of its customers could use its fixed-line network without any issues.
Deutsche Telekom, which owns a majority of T-Mobile US, services roughly 20 million fixed-network customers.
The cause of the outage is unknown, with those affected living in different areas and using different routers models, the comapany said.
"The attack attempted to infect routers with a malware but failed which caused crashes or restrictions for four to five percent of all routers", it said.
The attack involved Mirai, malicious software created to turn network devices into remotely controlled "bots" that can be used to mount large-scale network attacks, known as DDoS or distributed denial-of-service attacks.
But that number may be an underestimate: Since some of the affected routers also provide subscribers with telephone service, customers may have no way of letting the company know they are having difficulties.
As Krebs pointed out after his attack, the IoT revolution means that the world is flooded with all manner of vulnerable devices, using components that are easy for manufacturers to source.
Its network was not affected, it added. A user under the name "Anna-senpai" released the source code, saying: "Today, I have an incredible release for you".
"As more and more consumers bear the brunt of attacks through their internet providers and other suppliers, there will be mounting pressure for companies to make themselves more resilient".
Last month, the Mirai botnet caused a major headache in the United States, as millions of internet users lost access to a swathe of websites after an attack on Dyn.
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