Learn Spanish (Latin America): No le des la contraseña a nadie.

When telling someone not to do something (a negative command), Spanish uses a different verb form than it does for statements or positive commands. For the informal "you" (tú), negative commands are built using a form called the present subjunctive. Because dar (to give) is an irregular verb, its negative command form becomes no des (don't give).

Can I attach le to the end of the verb, like no desle?

No, pronouns can never be attached to the end of a negative command. They must always go between the no and the verb. You only attach pronouns to the end of affirmative (positive) commands, like dale (give it to him/her/them).

Why is there a le in this sentence if we already say a nadie?

This is a common Spanish quirk called a "redundant pronoun." Even though a nadie clearly states who shouldn't receive the password, Spanish still requires the indirect object pronoun le before the verb to point to that person. It is basically saying, "Don't to-them give the password to anyone."

Why does the sentence use both no and nadie? Doesn't that mean "Don't give the password to nobody"?