Viper is a UNIX-style bruteforce password cracker for passwords encrypted with crypt. It has been developed from Hale's viper 1.4 Perl program.

Usage:

Viper v1.6 (Hale 05/12/2000) - C version by Frank4DD (05/05/2014)
 Wiltered Fire - www.wilter.com/wf, incl. bugfixes by David C. Rankin
 
         -f     File to load password from (required unless using lsf)
         -u     Username to load from file (required unless using lsf)
         -lsf   Load saved file from previous session
         -pf    Save progress to file at update interval
         -rf #        Amount of time in hours to run for (default infinite)
         -c #         Character set from charset.ini to use (default 1)
         -pws #       Minimum password length (starting value, default 1)
         -pwl #       Maximum password length (default 8 - maximum 16)
         -ui #        Console update interval (in minutes - default 10)
         -v           Verbose output

Usage Example:

susie112:/home/me/viper-1.6/src # ./viper -f passwd -u root -ui 1 -v
 
 Viper v1.6 (Hale 05/12/2000) - C version by Frank4DD (05/05/2014)
 Wiltered Fire - www.wilter.com/wf, incl. bugfixes by David C. Rankin
 
 Found: user root pw:reUJbHrFWYCQk
 Found: Charset 0 in charset.ini
 ...command line parameters loaded.
 Character set is 93 chars long
 Starting crack on: Sun Oct  3 23:04:44 2009
 Cracking for pass length 1 (93 possibilities)
 Cracking for pass length 2 (8649 possibilities)
 Cracking for pass length 3 (804357 possibilities)
 Cracking for pass length 4 (7.48052e+07 possibilities)
 
 [ Length: | Last:    | CPS:    | Time Spent:      | Time Remaining:  | Done:  ]
 -------------------------------------------------------------------------------
 [    4    |     kq2r |  150000 | 000d:00h:01m:00s | 000d:00h:07m:18s | 12.03% ]
 
  The password has been located.
  Username : root
  Password : test
  Started  : Sun Oct  3 23:04:44 2009
  Finished : Sun Oct  3 23:06:30 2009
  Duration : 000d:00h:01m:00s
 
 Viper exiting...