Most of the hackers actually do not exactly know what is your password. But they start their efforts by cracking your password with variations of 10 common passwords we usally use.
They try get a hint either looking at your social network pages or with some other web hints.
The passwords, most of us adopt, are usually
1. Pet’s name
2. Significant dates (like date of wedding)
3. Date of birth or close relation
4. Child’s name
5. Other family member’s name
6. Place of Birth
7. Favourite holiday
8. Any favourite sport or player
9. Husband or wife name
10. Routine sequence number like 12345678
So if you have any or something like these passwords, change it immediately.