Hackers use several methods to gain unauthorized access to Facebook accounts. Here are some common techniques that cybercriminals use:

1. Phishing attacks: Phishing is a technique where an attacker creates a fake login page that looks like the original Facebook login page to trick users into revealing their login credentials. The attacker may send an email or message containing a link to the fake login page, Phishing attacks are one of the most common methods used to hack Facebook accounts. In a phishing attack, hackers create a fake login page that looks identical to the original Facebook login page. They then use various tactics such as sending emails or messages with a link to the fake login page, or creating fake websites with the same login page, tricking users into entering their login credentials. Once the user enters their login credentials, they are stolen, and the hacker can gain access to their Facebook account.

2. Password cracking: Another way hackers can hack into Facebook accounts is by using password cracking software. This software uses brute force attacks to guess the user's password by cycling through all possible combinations of characters until the correct one is found. Hackers can also use other methods such as dictionary attacks, which use pre-populated word lists of commonly used passwords and variations to try to guess the user's password.

3. Social engineering: With social engineering techniques, hackers manipulate people into giving away their Facebook login credentials willingly. This includes tactics such as posing as a Facebook employee or someone the user knows and trusts, or creating a sense of urgency or fear to trick the victim into giving up their login credentials.

4. Keylogging: A keylogger is a type of malware that records every keystroke made by the user, including their Facebook login credentials. Hackers can use a keylogger to install on the victim's device, and when the user enters their login credentials, the keylogger records them, and the hacker can use them to gain unauthorized access to the user's Facebook account.

5. Session hijacking: Session hijacking involves intercepting the user's session cookies, which are used by Facebook to verify the user's identity and keep them logged in. Once the hacker gains access to the cookies, they can use them to hijack the user's Facebook account and take control of it.

To prevent hackers from hacking into your Facebook account, you should avoid clicking on suspicious links, keep your password secure, enable two-factor authentication, and monitor your account activity regularly.