Offensive cyber warfare raises serious ethical problems for societies, problems that need to be addressed by policies. Since cyber weapons are so different from conventional weapons, the public is poorly informed about their capabilities and may endorse extreme ethical positions in either direction on their use. Cyber weapons are difficult to precisely target given the interdependence of most computer systems, so collateral damage to civilian targets is a major danger, as when a virus aimed at military sites spreads to civilian sites. Damage assessment is difficult for cyber war attacks, since most damage is hidden inside data; this encourages massive attacks in the hopes of guaranteeing some damage. Damage repair may be difficult, especially for technologically primitive victim countries. For these reasons, some cyber war attacks may be prosecutable as war crimes. In addition, cyber-war weapons are expensive and tend to lose effectiveness quickly after use as they lose the element of surprise, so the weapons are not cost effective.