what can a hacker do?

[Sergio]

A programmer with a certain skiil-set.
Nowadays, the terms "hacker" and "cracker" have been amalgamated into one known as a hacker. It used to be that a hacker was a specially gifted language programmer, efficient in optimizing programming functions and procedures. A cracker on the other hand, also a skilful professional, would be known for knowing the weak points in certain security systems and thus have the power to infiltrate said systems.
You are worried about somebody else compromising your internet social life.Being your x bf, he would probably know your passwords and sabotage your accounts. Create a new account or apply to fb to reset the account.
Always use complicated passwords (long + cap letters + small letters + numbers + special characters). The more intricate your password is, the harder it will be to crack your account.
Good luck