8. Is there a ban on anonymous donations to candidates?

Art 124.4 '5. The donations of natural or legal persons, including the contributions of the candidates, are documented in writing signed by the donor and the administrator electoral. In the case of gifts in kind, the supporting document must discriminate completely their number or quantity, their object and the value attributed to it, which can not be lower than its market value.' (Source Codigo Eleitoral 2010) 

No direct ban but implied