AckCmd is a client/server combination for Windows 2000 that lets you open a remote Command Prompt to another system (running the server part of AckCmd). It communicates using only TCP ACK segments. This way the client component is able to directly contact the server component through a firewall in some cases.
Running the AckCmd server part will create a backdoor into your computer! You should not use this tool for remote administration since it doesnt support neither authentication nor encryption.