Security Market Segment LS
Friday, 02 March 2018 11:03

GitHub hit by biggest ever DDoS at 1.35Tbps


The software hosting repository GitHub was totally inaccessible for five minutes on Wednesday evening US time, following what is claimed to be the biggest distributed denial of service attack ever recorded.

In a blog post, GitHub said while the attack, which peaked at 1.3 Tbps via 126.9 million packets per second, also rendered its servers intermittently unavailable for another four minutes, no data was compromised as a result.

Akamai, which does the job of content delivery network for GitHub, said it was able to mitigate the attack which is said to have been carried out through an amplification vector using memcached over UDP port 11211.

GitHub said such attacks worked by abusing memcached instances that were accessible on the Internet with UDP support enabled.

"Spoofing of IP addresses allows memcached’s responses to be targeted against another address, like ones used to serve, and send more data toward the target than needs to be sent by the unspoofed source," the company said.

Thus far, the biggest DDoS attack has been one which was close to 1Tbps against the French hosting provider, OVH. Concurrent attacks against the company in September 2016 clocked in at 990Gbps.

The attacks on OVH were launched using the Mirai botnet which is made up thousands of IoT devices.

Akamai said there were more than more than 50,000 known vulnerable systems exposed at this time which could be used to launch similar attacks.

The amplification factor could be manipulated by changing the values in an open server, Akamai said, thus making it possible for a 203 byte request to result in a 100MB response of reflected traffic, per request.

It said the way to counter this was by blocking port 11211. "By default, memcached listens on localhost on TCP and UDP port 11211 on most versions of Linux, but in some distributions it is configured to listen to this port on all interfaces by default," Akamai said.

Graphic: courtesy Akamai 


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Sam Varghese

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Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.



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