According to the third article of the Safety section in Facebook's Statement of Rights and Responsibilities, willfully compromising a user's account on the social networking constitutes a violation of Facebook's user agreement. Reporting such violations may be performed in a number of ways, depending on the situation. If either you or your friend's Facebook account has been hacked, file a report through Facebook's Help Center. If you are aware of a specific user on Facebook who is engaged in hacking other accounts, file a report regarding his activity through his profile page.
Report Your Compromised Profile
Go to Facebook.com, type the email and password associated with your account in the corresponding text fields and press "Enter."
Click "Account" in the top menu bar and select "Help Center."
Click "Security" in the "Popular Topics" section.
Click "I Think My Account is Compromised" in the Account Security menu.
Click either of the two security questions, depending on your situation, and click "Secure it here."
Click "Secure Account" and click "Continue."
Complete each of the steps for securing your account, including changing your password, changing your email password, reviewing your changes and unlocking your account. Click "Done" to complete the process. The developers at Facebook receive a notification regarding your account being compromised.
Report Your Friend’s Compromised Profile
Sign into Facebook, click "Account" in the top menu bar and select "Help Center."
Click the "Security" icon in the "Popular Topics" section.
Click "I Think My Friend's Account is Compromised" in the Account Security menu.
Click any of the three questions depending on your circumstances and click "File a Report."
Click your friend's full name, his birthday, the email associated with his account and a description of the situation in the corresponding text fields.
Click "Submit" to send the report to the developers at Facebook.
Report a Profile on Facebook
Log into Facebook, click the "Search" text field and type the name of the profile you want to report for hacking.
Scroll down and click "Report/Block This Person" in the left side bar.
Click "Unfriend" or "Block" depending on the situation and click "This Person is Bullying or Harassing Me," click the drop-down menu and select "Other." Facebook does not offer an option in this drop-down menu that applies specifically to hacking, but selecting this option is the best fit for that form of violation.
Click the user's name at the top of the page, type a report regarding the account hacking in the text field and press "Enter." The report is sent to the Facebook developers.