Memcached is a popular caching system, but if improperly configured, it can be vulnerable to UDP-based attacks. This guide explains how to secure your Memcached server by disabling the UDP protocol and restricting access to local connections.

Why Secure Memcached Against UDP Attacks?

UDP (User Datagram Protocol) is less secure compared to TCP (Transmission Control Protocol). Attackers can exploit the UDP protocol on Memcached servers for amplification attacks, leading to significant network disruption. By restricting the server to use TCP and limiting its accessibility, you can greatly enhance its security.

Steps to Secure Your Memcached Server

1. Restrict Access to Localhost

If your Memcached server is only used locally, you can configure it to listen only on the local loopback address (127.0.0.1) and disable the UDP protocol. This ensures the server is not exposed to the internet.

Edit the Configuration File

1. Open the Memcached configuration file using a text editor:

nano /etc/sysconfig/memcached

2. Add the following line under the OPTIONS section:

OPTIONS="-l 127.0.0.1 -U 0"

After editing, the configuration file should look like this:

PORT="11211"

USER="memcached"

MAXCONN="1024"

CACHESIZE="64"

OPTIONS="-l 127.0.0.1 -U 0"

2. Disable UDP for Remote Bindings

If your Memcached server is accessible via a specific IP address (other than 127.0.0.1), you can disable UDP by modifying the OPTIONS line:

OPTIONS="-U 0"

3. Restart the Memcached Service

After making the changes, restart the Memcached service to apply the new configuration:

service memcached restart

That’s It!

By disabling UDP and limiting Memcached to local connections, you effectively mitigate the risk of UDP-based amplification attacks.