I don't consider "etw./sich gegen etw. od. vor etw. sichern" to be idiomatic German usage. I would classify "sichern vor" as an error in grammar. "sichern gegen", is used only in military parlance and only in relation to an object (die Kaserne gegen Angriffe sichern). In common parlance, "sichern" is used without complement at all (see http://www.duden.de/rechtschreibung/sichern#B...),

As a reflexive verb it's either "sich gegen etw. absichern" or "sich etw. sichern" (anglicism for "to secure sth." = to succeed in obtaining sth., e.g. "sich Karten für das Konzert sichern")