Attackers abused vulnerable Memcached Servers to launch high-bandwidth DDoS attacks and there is a huge increase observed in this attack vector.

Memcached is a memory caching system used to speed up a dynamic database of the websites by caching the data in RAM which can increase the loading time by reducing the number of times an external data source must be read.

It is a middleware so it lacks access controls and it should not be exposed to the public Internet, according to Shodan reports there are around 88,000 open Memcached servers found.

If the UDP port(11211) is opened then attackers can exploit by sending thousands of forged requests to a vulnerable UDP server and servers process the request without knowing it is forged one, which results in overwhelming of its resources.

Cloudflare says a carefully carfted technique allows an attacker with limited IP spoofing capacity (such as 1Gbps) to launch very large attacks (reaching 100s Gbps) “amplifying” the attacker’s bandwidth.


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According to DDoS Threat Landscape, the Memcached graph is almost flat and the spike is only just for a couple of the days.

Memcached Servers

Cloudflare says at peak it generated 260Gbps of inbound UDP traffic and the majority of the packets size is 1400 bytes. Doing the math 23Mpps x 1400 bytes gives 257Gbps of bandwidth.

Launching the attack is quite simple, all attacker need is to embed a large payload on an exposed Memcached server and then the attacker spoofs the “get” request message with target Source IP.

The Vulnerable Memcached servers present all over the globe and according to Shodan search reports, there are 88,000 open Memcached servers.

Memcached Servers

Security researchers recommended disabling the UDP support if it is not in use and to place the Memcached servers behind the Firewall. Also, it is recommended to specify Memcached servers to listen only on localhost.

Reports on Memcache DDoS Attacks published by Cloudflare and arbornetworks.


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