Secure opening of ports
I posted before on the idea of opening, say the SMTP port briefly,
periodically to recieve any email addressed to my server. I had knockd, the
very cute port-knock daemon recommended. Of course, if I am doing the
knocking, this will work. A server, SMTP, HTTP, etc., must be always open or
openable under the right and secure circumstanced.
Two examples are given in the knockd configuration. The first opens of port
after a sequence of "knocks". The second opens it for a period of time.
1. From an outside machine, say using openSSH, how do I configure to do this
sequence and open my home machine's SSH port?
2. How might I keep a secure SMTP port available when needed but hidden
otherwise using knockd's 2nd example? or the brief periodic opening I first