Comment by dpritchett

For the security novices amongst us: I had no idea how to do this so I figured out a quick python script to test it:

    >>> from hashlib import sha1
    >>> def check_pass(plaintext, offset=5):
    	hashed = sha1(plaintext).hexdigest()
    	return (hashed, '0' * offset + hashed[offset:])

    >>> check_pass("linkedin")
    ('7728240c80b6bfd450849405e8500d6d207783b6',
     '0000040c80b6bfd450849405e8500d6d207783b6')

Edit: I'm pretty sure JtR refers to this: http://en.wikipedia.org/wiki/John_the_Ripper