PuttyHijack is a POC tool that injects a dll into the Putty process to hijack an existing or soon to be created connection. This can be useful during penetration tests when a windows box that has been compromised is used to SSH/Telnet into other servers. The injected DLL installs hooks and creates a socket in guest operating system for a callback connection that is then used for input/output redirection. It does not kill the current connection, and will cleanly uninject if the socket or process is stopped.
Source: https://thehackernews.com/2011/10/proof-of-concept-puttyhijack-hijack.html