How can my server be DNS spoofed?

First off, a critically important question: have you moved your domain name from one server to another in the last day or two? Or, perhaps, has your ISP moved you from one server to another and therefore had to change your IP (internet protocol) address?

That's what's happening. Your Mac remembers that you used to end up at, say, 129.1.1.30 when you requested to connect using the secure ssh protocol, but now the domain name resolves to a different IP address.

Here's the message you're probably seeing:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
The RSA host key for intuitive.com has changed,
and the key for the according IP address 205.212.166.171
is unchanged. This could either mean that
DNS SPOOFING is happening or the IP address for the host
and its host key have changed at the same time.
Offending key for IP in /Users/taylor/.ssh/known_hosts:4
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
ce:a1:ce:c7:90:15:41:c4:ac:81:5f:a3:f9:7d:97:1d.
Please contact your system administrator.
Add correct host key in /Users/taylor/.ssh/known_hosts to get rid of this message.
Offending key in /Users/taylor/.ssh/known_hosts:1
RSA host key for intuitive.com has changed and you have requested strict checking.
Host key verification failed.

Pretty scary!

But you can see that it shows you the solution if you're confident that you are pointing at a new IP address and all is well: simply wipe out the "known_hosts" file for that connection in your "ssh" configuration folder (in my case, it's /Users/taylor/.ssh).

You can either just remove the offending line or delete the entire file and let it reprompt you whether to save the secure keys for other sites you visit too. I usually opt for the latter.

If you haven't made any changes, then you need to get on the phone with your Internet Service Provider ASAP to figure out what's going on!

Hope that helps clear things up!