The middle finger is a silent way to tell someone to f&%# off in the United States. Other countries have their own versions of the “middle finger”.
For instance, giving the old “thumbs up” to anyone is considered to be an extremely lewd gesture. Instead of giving the thumbs up, just do nothing. Iran is another country with constantly changing regimes. Depending on who is in charge, you may be faced with different punishments just for giving the thumbs up. It is probably best to keep your hands at your side.