Secure network coding assumes that the underlying network links are lossless, thus it can be applied over lossy networks after channel error correction. Yet it is well known that channel losses, such as packet erasures, can be constructively used for secrecy over a link. We address here the challenge of extending these results for arbitrary networks. We provide achievability schemes over erasure networks with feedback, that outperform the alternative approach of channel error correction followed by secure message transmission separation. We show optimality of our proposed scheme in some special cases.