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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: 0) by Anonymous Coward on Monday March 25 2019, @12:03PM (1 child)
As far as developers go, he's such an incredibly somber person that you have to watch your time going to his site. There's great fun and insight to be had checking-up on his projects and experiments from time to time. Check out his work on hash-functions after you spent some time with endlessh.
(Score: 2) by driverless on Tuesday March 26 2019, @10:36AM
In this case, unfortunately, it's relying on a quirk of badly-written software, I assume OpenSSH since that's the de facto standard. I've just connected with the SSH client I use and got.. hmm, closed the window, something like "Server sent excessive amounts of data without an SSH ID string", all in a fraction of a second. So it's an exploit of an OpenSSH (?) bug more than anything else.