Shimmer

Shimmer is an impressive Perl implementation of the C3PO proposal, designed to conceal a critical server by employing a changing set of ports. This software comprises a client and server program that act as an efficient alternative to programs like tumbler for port knocking. Shimmer is especially useful for hiding high-value ports such as web servers and SSH on public IP addresses while interchanging a set of 16 cryptographically encrypted ports. One of these encrypted ports forwards to the actual service, while the other 15 lead to a blacklist trap for attackers, making it nearly impossible for any attacker to access the real port.

With Shimmer, both the client and server must synchronize to the nearest minute, effectively holding 48 ports open at every moment (16 per minute). This ensures that the software works seamlessly, preventing problems due to small changes in clock drift.

Using Shimmer is simple and straightforward. The shimmerd program, a daemon that manages the mirages (i.e., collections of ports) on a server, is configured using a simple text-based file. A mirage is defined for every unique name, each containing settings such as secret, port number, and range. The secret is a shared password between Shimmer and any user who connects using the client program.

To use Shimmer, one only needs to input the mirage name and range of ports configured on the server through the client program. The legitimate port is then outputted and can be used to configure other programs. For instance, when connecting to an SSH server, the user can include the generated port in the SSH command to make a secure connection.

Overall, Shimmer is a stable and straightforward to use software with impressive features for port hiding, making it an ideal choice for anyone seeking a robust port security system.