WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!

This warning is raised when you try to ssh to a linux box. Most probable reason for this warning is the change in host key

I am assuming that the IP address is aa.bbb.ccc.dd

$ ssh root@aa.bbb.ccc.dd
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    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 a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
13:74:ce:b4:65:09:75:0c:80:1a:0c:0b:69:c0:68:f1.
Please contact your system administrator.
Add correct host key in /Users/wmalik/.ssh/known_hosts to get rid of this message.
Offending RSA key in /Users/wmalik/.ssh/known_hosts:32
RSA host key for 10.201.127.21 has changed and you have requested strict checking.
Host key verification failed.

Fix:

Run the command below to fix

ssh-keygen -R  aa.bbb.ccc.dd