A Defence inquiry into a rogue Afghan soldier's murder of three Australian soldiers is highly critical of the "relaxed" security at the time of the attack.

Vice Chief of the Defence Force Air Marshal Mark Binskin says there were shortfalls in protection and decisions made on the ground, but acknowledged that greater security still may not have prevented the deaths of Lance Corporal Stjepan Milosevic, Sapper James Martin and Private Robert Poate.

"No matter how much you put in place you can never, 100 per cent, stop someone trying to commit a crime like this," he said.

"You can mitigate the risk as best you can but I don't believe you could ever stop someone who is intent on doing this."

Air Marshal Binskin said insider attacks remained a complex and evolving threat.

The three men died and two other diggers were injured when Afghan sergeant Hekmatullah fired 10 to 15 automatic rounds at Australian soldiers who were playing cards inside a patrol base 20km north of Tarin Kowt in Oruzgan province on August 29, 2012.

Air Marshal Binskin said the inquiry into the attack highlighted serious issues and made six recommendations to which defence has agreed.

Four relate to possible administrative action against three ADF members, including the patrol commander, which the chief of the defence force has referred to the chief of army for consideration.

The fifth concerns instant response capability that has been implemented and the sixth is that a commission of inquiry was not warranted.

Air Marshal Binskin said the decisions and actions made at the time were at the minimum level of authorised force protection to provide security for the soldiers.

"However, they did not adequately address the specific situation at the patrol base, that potentially placed personnel at significant risk to the threat of fire."

The inquiry officer found the decision to adopt a relaxed level of security was not in accordance with orders and meant the troops were not ready.

Some soldiers were dressed in gym gear and not wearing body armour. Two soldiers have since been disciplined over their inappropriate dress.

Air Marshal Binskin said it wasn't possible to make a link between protection arrangements and the reasons behind the insider attack.

"There were no weaknesses or deficiencies in our intelligence preparation and no information to Australian or coalition forces to suggest Hekmatullah was a threat to Australians," he said.

"In fact, his existence was unremarkable from a personnel or intelligence perspective."

He said they may never know what prompted the attack but bringing Hekmatullah to justice remained a key focus.

"Let me assure you, we will not let this go."