[bonzini]

There used to be a hypothesis that DNA originated in viruses and that the three branches of life (archea, bacteria and eukaryota) evolved when three different DNA viruses encountered preexisting RNA-based cells. (https://www.pnas.org/content/103/10/3669)

Nowadays however it is more widely believed that eukaryota descend from archea, but anyway it's pretty much a given that viruses are not and have never been alive. And while the opposite has happened, gene transfer usually goes from viruses to cells, endowing them with new abilities, more than the opposite direction.