"Trick 5: SSH back door
Many times I'll be at a site where I need remote support from someone who is blocked on the outside by a company firewall. Few people realize that if you can get out to the world through a firewall, then it is relatively easy to open a hole so that the world can come into you.
In its crudest form, this is called "poking a hole in the firewall." I'll call it an SSH back door."
