A major cybersecurity attack left a number of popular sites including Reddit, Twitter and Spotify down for most of the morning on Oct. 21.
The impacted sites were all clients of the network infrastructure company Dyn, and had their services disrupted by what's known as a distributed denial of services (DDoS) attack. To execute DDoS attacks, hackers take control of a large number of machines -- often PCs and mobile devices infected with malware -- and use thousands of those compromised machines, known as bots, to flood the target servers with data requests.
By overwhelming the target servers with more requests than they can handle, hackers can successfully make web services unavailable to the users they're intended for, which is what happened for about two hours on the morning of Oct. 21.
"This attack is mainly impacting U.S. East and is impacting Managed DNS customers in this region," Dyn wrote in a statement as the attacks occurred. "Our Engineers are continuing to work on mitigating this issue."
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Most services were restored by 9:20 a.m., according to UPI.
Amazon.com was also impacted, although it wasn't clear if that attack was related to the others.
"We provide service to Amazon but theirs is a complex network so it is hard to be definitive about causality at the moment," Doug Madory, director of internet analysis at Dyn, told Reuters.
The attack comes a week after the U.S. Department of Homeland Security warned that hackers were assembling "bot armies" -- sometimes also called "zombie congas" -- by infecting not only traditional computing devices, but also smart TVs, routers, printers and other devices capable of accessing networks.
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Brian Krebs, who operates the blog Krebs on Security, noted the DDoS attack came only a few hours after Madory delivered a talk on DDoS security at a meeting of the North American Network Operators Group in Dallas, Texas.
Krebs echoed Homeland Security in his concern about the ease of hacking connected devices.
"The size of these DDoS attacks has increased so much lately thanks largely to the broad availability of tools for compromising and leveraging the collective firepower of so-called Internet of Things devices -- poorly secured Internet-based security cameras, digital video recorders (DVRs) and Internet routers," he wrote.