Memcrashed – Major amplification attacks from UDP port 11211

CC BY-SA 2.0 image by David Trawin
Over last couple of days we've seen a big increase in an obscure amplification attack vector - using the memcached protocol, coming from UDP port 11211.
In the past, we have talked a lot about amplification attacks happening on the internet. Our most recent two blog posts on this subject were:
- SSDP amplifications crossing 100Gbps. Funnily enough, since then we were a target of an 196Gbps SSDP attack.
- General statistics about various amplification attacks we see.
The general idea behind all amplification attacks is the same. An IP-spoofing capable attacker sends forged requests to a vulnerable UDP server. The UDP server, not knowing the request is forged, politely prepares the response. The problem happens when thousands of responses are delivered to an unsuspecting target host, overwhelming its resources - most typically the network itself.

Amplification attacks are effective, because often the response packets are much larger than the request packets. A carefully prepared 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.
Memcrashed
Obscure amplification attacks happen all the time. We often see "chargen" or "call Continue reading
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