A trusted friend and I had ssh'ed into a Mac OS X Web Server (either 10.6.8 Snow Leopard or 10.7 Lion) from two different locations. Then my password stopped working when trying to log in.

I can safely rule out the possibility that my friend changed my password, and I’m pretty sure another malicious user didn't do it. The only thing my friend did was send his SSH key pair to the server.

Somebody else set up the server so I am not sure how everything is configured, but is there a security measure employed by mac servers that kicks users who are logging in from two different IPs at the same time?


It is a control that could have been added by the admins on that server - concurrent logins (except where this expected) are a simple flag to alert of possible malicious behaviour.

However, it is not something we see that often, and very rarely at system level - this is usually an application based control - so I would be more inclined to think that somewhere along the line something has just got broken, whether this is a password expiry, account disabling for some other reason, incorrect keypairs being used, or even configuration settings being set up incorrectly when your friend did that.

There are a lot of good reasons to avoid sharing accounts, and not just for the sysadmins - you might need to go through the history file on your friend's machine to see exactly what happened at his end.

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