  With over 750 million active users, Facebook is the most famous social
networking website. One particular aspect of Facebook widely discussed in the
news and heavily researched in academic circles is the privacy of its users. In
this paper we introduce a zero day privacy loophole in Facebook. We call this
the deactivated friend attack. The concept of the attack is very similar to
cloaking in Star Trek while its seriousness could be estimated from the fact
that once the attacker is a friend of the victim, it is highly probable the
attacker has indefinite access to the victims private information in a cloaked
way. We demonstrate the impact of the attack by showing the ease of gaining
trust of Facebook users and being befriended online. With targeted friend
requests we were able to add over 4300 users and maintain access to their
Facebook profile information for at least 261 days. No user was able to
unfriend us during this time due to cloaking and short de-cloaking sessions.
The short de-cloaking sessions were enough to get updates about the victims. We
also provide several solutions for the loophole, which range from mitigation to
a permanent solution
