John the Ripper, also know as john in yum & apt package managers, is an open source password cracker and hash decipher program.
Here is a “How To” tutorial for using John the Ripper on VPS or Dedicated instances so that you can leave it running overnight, for example.
John the Ripper CentOS & Fedora installation & usage:
# john requires openssl-devel package
yum install openssl openssl-devel -y
# get the latest JUMBO version of John
wget http://www.openwall.com/john/j/john-1.8.0-jumbo-1.tar.gz
# extract and enter the src folder
tar -xzvf john*
cd john*
cd src
# configure and make john
./configure && make
# navigate and run the test and benchmark script
cd ../run
./john --test