CNET has an educational movie (4:21 min) how to recognize, avoid and clean up:

here are some categories of intrusion, which you might face with your use of Facebook:

https://nakedsecurity.sophos.com/2011/02/21/i-accepted-a-fake-facebook-friend-request-should-i-be-afraid/

• Stalker.
• Identity thief. Your bogus Facebook friend may be interested in your profile because of the information you might be sharing up there
• Spammer/Malware author.
• Scammer.

If you want to learn more about threats on Facebook, join the Sophos Facebook page where more than 100,000 people are benefiting from early warnings about the latest attacks.

here some general idea of the different types of Facebook viruses:

Remove Facebook virus, removal guide – 2-Spyware.com

Facebook Child Porn virus

Facebook Change Color virus

Facebook Friend Request virus

Facebook Automatic Wall Post virus

Facebook Message virus 

Invitation Facebook virus

Facebook Stalker virus 

Facebook “hahaha” virus

Facebook video virus

here are steps, which you can take to clean up the damage:

How to Clean up a Facebook Virus

Remove Facebook virus, removal guide – 2-Spyware.com

How to remove Facebook virus?

If you want to avoid Facebook virus, you MUST avoid clicking on links that are not legitimate. If you are not expecting a message from your friend, you should simply ignore it or send him/her a message FIRST and ask if he/she has sent something to you. Additionally, avoid accessing every game or other app on Facebook because it may be hacked by cyber criminals. If you have been tricked by any of these types of Facebook virus, you should change your Facebook’s password ASAP in order to avoid identity theft in the future. Additionally, conatct your friends and warn then that your account has been hacked. Finally, download Reimage or Malwarebytes Anti Malware, update it and run a full system scan in order to make sure that your PC is free of viruses…