Drosera

Drosera is a small SSH tarpit server. Inspired by endlessh.

When initiating a SSH session, the server first sends a version string to the client before communication begins. However, tarpits like drosera can exploit the following paragraph in the SSH specification, found in RFC 4253:

The server MAY send other lines of data before sending the version
string.  Each line SHOULD be terminated by a Carriage Return and Line
Feed.  Such lines MUST NOT begin with "SSH-", and SHOULD be encoded
in ISO-10646 UTF-8 [RFC3629] (language is not specified).  Clients
MUST be able to process such lines.

It is thus incredibly easy to trap ill-configured clients in a tarpit by simply never sending the version string. To keep the connection alive, some data should be sent periodically.

Drosera, like its beautiful namesake, is designed to thrive in memory-constrained environments while feeding on the numerous blood-sucking drones seeking prey on the Internet.

Risks

I do not recommend running drosera on anything valuable. Running tarpits servers at all might not be a good idea so make sure you know what you are doing. Worst case scenario an adversary could exploit a vulnerability in drosera to gain access to machine it's running on. Adversaries could also launch massive denial-of-service attacks, quickly consuming what little memory is available and crashing the server.