No, we’re not telling you how to know if your friends are real or not. And we’re not talking about some translation spy who pretends to like you, Mr./Ms. Translator, while s/he steals all your tricks.
‘False friends’ is an actual term coined in 1928 to identify those words that sound or look alike in different languages but have significantly different meanings.
If you have just cracked a joke that made a lovely young Spanish lady blush, it would be best not to tell her, ‘Te ves embarazada,’ or you might get slapped. You just told her she looked pregnant when you meant to say, ‘You look embarrassed.’ Voila! A false friend!