An almost invisible ssh connection

In the worse case if you have to ssh on a box, do it every time
with no tty allocation

ssh -T user@host

If you connect to a host with this way, a command like "w" will not
show your connection. Better, add 'bash -i' at the end of the command to
simulate a shell

ssh -T user@host /bin/bash -i

Another trick with ssh is to use the -o option which allow you to
specify a particular know_hosts file (by default it's ~/.ssh/know_hosts).
The trick is to use -o with /dev/null:

ssh -o UserKnownHostsFile=/dev/null -T user@host /bin/bash -i

With this trick the IP of the box you connect to won't be logged in
know_hosts.

Using an alias is a good idea.

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credits: An artical by Duvel in phrack magazine
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