Social media users who use tweets and online posts to comment on a military operation could be regarded as legitimate military targets.

Australian army Land Warfare Studies Centre analyst Chloe Diggins on Thursday said a recent social media war between Israel and Hamas raised complex ethical questions about who was a combatant and therefore a legitimate military target.

A key question was whether such comments constituted an act of war.

"If that's the case, this might mean that those using social media in support of military operations are now legitimate targets," she wrote in a blog for the Australian Strategic Policy Institute.

The Geneva Convention defines legitimate military targets as objects "which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralisation, in the circumstances ruling at the time, offers a definite military advantage".

The convention protects civilians unless they are taking a direct part in hostilities.

"So if social media operators or users engage in the conflict by uploading, downloading, sharing, or otherwise adding to content in any way, they then become actors contributing to hostilities," Ms Diggins said.

"In doing so, civilian social media users lose their protected status and can become legitimate targets."

Ms Diggins said if a country could declare war over Twitter - as Israel did when it announced the start of recent hostilities - who's to say Twitter users could not "fight" in the information space of that war?

"Moreover, who's to say they shouldn’t reasonably expect to become legitimate targets themselves?" she said.Ms Diggins stressed her views did not reflect those of the Australian Defence Force.

AAP