When you are SSHing into virtual machines on a daily basis this message tends to get annoying:

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@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
The RSA host key for XXX has changed,
and the key for the corresponding IP address XXX.XXX.XXX.XXX
is unknown. 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.
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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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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
XXXX.
Please contact your system administrator.
Add correct host key in /Users/XXXX/.ssh/known_hosts to get rid of this message.
Offending key in /Users/XXXX/.ssh/known_hosts:28
RSA host key for XXXXXX has changed and you have requested strict checking.
Host key verification failed.

YUCK! You might get tired of editing the ssh known_hosts file and removing the offending line, but there is an easier way. Use ssh-keygen. If you know the host is bobby.example.com then just run

$ ssh-keygen -R bobby.example.com

And you're done!