As with most cheaters, people who use Facebook for illicit affairs are ready to defend themselves—and perhaps even blame you for acting weird, disconnected, and whatever they deem as suspicious behavior. If you question any of their activities or behavior, they will likely shift the blame, manipulate the conversation, deflect your accusations, get angry and defensive, or leave.

While these signs aren't a 100% foolproof way of detecting if your partner is Facebook cheating, they are sure signs that something serious is off in your relationship. Bottom line: Follow your gut instincts.