Usage

./sshdos -t <host>[:port]

Options:

  -c int
    	number of connections to initiate (default 100)
  -t string
    	target "host" or "host:port" (required)
  -u string
    	user to ssh as; probably doesn't matter (default "root")

About

Very basic proof of concept for SSH denial of service.

Related OpenSSH Settings: MaxStartups, LoginGraceTime, MaxAuthTries. (PerSourceMaxStartups as of 8.5)

Notes

setting MaxStartups to larger values (eg. >1000) may cause high memory usage (>1GB) due to fork()ing in the connection handler.

fail2ban probably helps too.