Hydra is a tool that can guess/crack valid login/password pairs extremely quickly. It supports a great deal of protocols. Variant exist both for Windows and Unix.
Currently Hydra supports attack against the following services:
TELNET, FTP, HTTP, HTTPS, HTTP-PROXY, SMB, SMBNT, MS-SQL, MYSQL, REXEC, RSH, RLOGIN, CVS,
SNMP, SMTP-AUTH, SOCKS5, VNC, POP3, IMAP, NNTP, PCNFS, ICQ, SAP/R3, LDAP2, LDAP3, Postgres,
Teamspeak, Cisco auth, Cisco enable, LDAP2, Cisco AAA
Installation:
./configure
make
make install
Pre-requisites:
libssh2
libssh2.so may need to be linked from its installed location to /lib so Hydra detects it when trying to crack ssh.