Why is my login banned ("connection refused") on the Sherlock cluster?


I have been successfully connecting with ssh to the Sherlock cluster, with a command like this:

 ssh -Y <username>

I’ve recently been seeing this error:

ssh: connect to host port 22: Connection refused

I’m not sure what is wrong, because it was working before!



In order to prevent malicious behavior like spamming a login (multiple repeated attempts) to guess a password, the Sherlock cluster will automatically ban you if you try too many times! The behavior you are seeing is likely due to:

  1. some application trying repeated attempts on your behalf, and your login (ip address) getting temporarily banned
  2. incorrect credentials

1. Repeated Attempts by an Application

Here is a likely situation where you could run into trouble! If you use a Macbook, it will go to sleep after some time. If you also use sshfs when the computer goes to sleep, it might try to reconnect you, and fail because you aren’t completing the two factor authentication. This would lead to many attempted failures, and your ip address being banned. The ban is temporary, so you might consider taking a break to try again later. In the future, you should disconnect SSHF mounts. If you are looking for other alternatives for login, it’s also good to check for updated information on the page for alternative login options.

2. Incorrect Credentials

It could actually be the case that you specified your username or password incorrectly, and this is the reason for your IP address being denied. You can check with research computing to ensure you are using the proper sunetid.

If you would like further instruction or clarification on this answer, please reach out to us at with “AskCI” in the subject tag. Be sure to link to this post so we can respond here promptly.