This is a regular verb. It follows the conjugation pattern of the verb falar.
This verb is very common in informal Brazilian Portuguese. It is rarely used in Portugal, where alternatives like 'contar' or 'denunciar' are more natural.
Present:
Ele sempre dedura os colegas de classe.
He always snitches on his classmates.
Preterite:
Ontem você me dedurou para o chefe.
Yesterday you snitched on me to the boss.
Present Subjunctive:
Espero que ninguém nos dedure.
I hope no one tells on us.