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Software engineer Chris Wellons writes about tar-pitting nefarious SSH probes. Anyone with a publicly-facing SSH server knows that it is probed from the moment it is turned on. Usually, the overwhelming majority of incoming connection attempts are malevolent in nature. There are several ways to deal with these attempts, one method is to drag out the response for as long as possible.
This program opens a socket and pretends to be an SSH server. However, it actually just ties up SSH clients with false promises indefinitely — or at least until the client eventually gives up. After cloning the repository, here’s how you can try it out for yourself (default port 2222):
[...] Your SSH client will hang there and wait for at least several days before finally giving up. Like a mammoth in the La Brea Tar Pits, it got itself stuck and can’t get itself out. As I write, my Internet-facing SSH tarpit currently has 27 clients trapped in it. A few of these have been connected for weeks. In one particular spike it had 1,378 clients trapped at once, lasting about 20 hours.
(Score: 3, Informative) by NateMich on Monday March 25 2019, @06:00PM (1 child)
Stop using port numbers with "22" in them. Those are targeting by scans almost as much as the actual ssh port, 22 is. Trust me. Be random.
(Score: 3, Informative) by maxwell demon on Monday March 25 2019, @07:37PM
So if you've got a reason to have a real sshd on port 22, it might be a good idea to tarpit all the other ports with "22" in their number?
The Tao of math: The numbers you can count are not the real numbers.