How do you stop a Belgian Malinois from biting?

The moment a Belgian Malinois tries to bite, scold and stop it at once. If it disobeys, pull the leash firmly or tap its mouth, then praise and treat it once it calms down. If it is aggressive toward strangers, have a friend help train: after stopping the biting attempt, let the friend offer food.

Because the dog sees the food coming from the friend via you, it relaxes its guard. Over time the Malinois gets used to strangers approaching.