THC-Hydra is a high quality parallelized login hacker for Samba, Smbnt, Cisco AAA, FTP, POP3, IMAP, Telnet, HTTP Auth, LDAP, NNTP, MySQL, VNC, ICQ, Socks5, PCNFS, Cisco and more. Includes SSL support, parallel scans, and is part of Nessus.