My Facebook account is cracked...

Yesterday night after using the internet, I immediately went to bed but before I try to update the status in facebook mobile, but apparently I can not, even though the correct password is entered, tried many times still can not, I finally went to sleep aja, tried only in the PC.
The next day, I try on PC, same result ... the result : (, And then I open the e-mail account that is used to facebook, there is notification of the security warning that the contents facebook:

We have detected Suspicious activity on your Facebook account and have your password reset as a security precaution. It is possible that malicious software was downloaded to your computer or that your password was stolen by a phishing website designed to look like Facebook .........

They ordered to me to change my password and update antivirus and finally I am trying to do, this time using the password with a combination of letters numbers, which he said was powerful and the password is longer than before and this time, thanks god, facebook can be accessed again.
I just could not get it, a friend who chat with last night also experienced the same thing, I suggest doing the same thing with. can this mass attack? ... hehehe. A friend on FB also recommend changing your password often, I thought this great idea, and I also remember about cookies and privacy settings enter the firefox, I finally find the "accept third party cookies' option that by default there is still mark, then I removed signs mark because I suspect this is the cause, my facebook is cracked, I also set "keep until" to "close firefox", but cookies also more important for adsense program, banking site, webmail, etc. My suggestion, activate them if you just need it and dont activate cookies in fake sites, porn sites, etc.