TCP Port 11211 – Memcached

Memcached is a high speed memory caching system that websites and applications use to take load off their databases. It was designed for trusted internal networks, so it ships with no authentication and no encryption. Anyone who can reach the port can read or change whatever the cache holds.

About TCP Port 11211

Port 11211 is registered with the Internet Assigned Numbers Authority (IANA) for memcache. The IANA description reads: ‘Memory cache service’.

Security Considerations

Memcached should never be reachable from the public internet. Exposed instances leak whatever data passes through the cache, and the UDP side of the service was the engine behind some of the largest amplification attacks ever recorded, where tiny spoofed requests triggered enormous responses aimed at a victim. Modern builds disable UDP by default, but older and misconfigured servers are still probed for it constantly. Bind memcached to localhost or a private interface, firewall the port, and use SASL authentication where the deployment supports it.

Data Sources

This information is compiled from: IANA Service Name and Transport Protocol Port Number Registry.