I am trying to recover a password that I have lost a few years ago.
- I know for a fact my password contained 8 characters and the first 4 are letters (could be lowercase or uppercase meaning AbCd, ABCD, Abcd, or abCd)
- The last 4 are numbers (from 0-9)
What I did to calculate how many possibilities there is, is multiply 26 x 2 = 52 (alphabet times 2 because upper and lowercase), I then used the nCr formula, 52 C 4 = 270725, knowing that the first four characters are letters. Used the same formula, 10 C 4 = 210 which is the last 4 numbers. After that I multiplied 270725 by 210 which is 56,852,250 different combinations.
My question now is what program or how can I possibly generate those passwords.
The program you are looking for is John the Ripper. It's a free password-cracker software that allows you to fine-tune which password it tries, and in which order (starting with more likely password, and ending with less likely ones). Here is a tutorial on how to setup a rule-based "attack" with JtR.