What sci-fi show was based in space and there was an enemy ship that had abandon all hope written on it.?

I remember watching it when I was younger (I'm 22 now) and there was a single enemy ship that was attacking and they had no idea who or what it was and I believe it had "Abandon all Hope" written on it even though the enemy wasn't human. Any ideas? I'm thinking Battlestar Galactica or Babylon 5.