This is the sort of thing I've considered doing, but I've worried about locking myself out, if I'm trying to connect remotely and having a particularly bad case of clumsy typing.
A similar example to my worry follows.... it's a very interesting idea, but I wonder what procedures you have in place to prevent the following??
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Sancho:> Hey, orangesquid, can you check out something on sancho3 for me, in /var/log?
orangesquid:> sure, let me open a shell
os@orangesquid.net:~$ ssh sancho3.sancho.com
Resolver timed out
os@orangesquid.net:~$ grep sancho3 ~/sancho-hosts
11.22.33.49 sancho3
os@orangesquid.net:~$ ssh 11.22.33.46
^C "Dammit, clumsy hands"
os@orangesquid.net:~$ ssh 11.22.33.49
Connection timed out
os@orangesquid.net:~$ ping 11.22.33.49 -c3
Ping 11.22.33.49 (64 bytes) from 99.88.77.66
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4 packets transmitted, 0 packets received
"Stupid auto-block..."
os@orangesquid.net:~$ mail sancho2000@gmail.com
Hey, can you unblock me? Typo!
.
os@orangesquid.net:~$
MAIL FROM: postmaster@sancho.com
You attempted to send mail to "sancho2000@gmail.com" from 99.88.77.66. This IP address has been banned. Sorry.