The first thing you must do if you suspect that your Facebook account has been compromised is to change your password. Then, if you are using Facebook for logging into apps such as Spotify or Instagram change your logins as well. This will prevent the hacker from accessing the third-party apps through your compromised Facebook profile.
Hackers can find a wealth of personal information in hacked Facebook accounts. Hackers could utilize this information for fraudulent purposes, such as stealing credit card numbers and spamming people with fake credit card offers or phishing scams. They can also use the compromised account to send spammy messages to friends, or publish on your timeline using your name (as as if you had done it yourself).
Hackers are likely to gain access to accounts through exploiting a weakness in the Facebook app code. A bug in the iOS Facebook application allows hackers to steal cookies, and then steal the “access token” of an iPhone user. These tokens are digital keys, give the hackers full control over the user’s Facebook Account, and any other websites they access using their Facebook credentials.
Hackers may also gain account access by using brute-force attacks. This method involves figuring out a password, typically the most commonly used ones like 123456789, or 1234567890. Hackers can also gain access to accounts by scanning compromised credentials. There are several tools for free that can be used to check for stolen information, such as a popular website called HaveIBeenPwned.