An inquiry into the deaths of three soldiers at the hands of an Afghan National Army soldier is highly critical of short-falls in force protection, defence says.
The report on the insider attack, released on Wednesday, makes 22 findings of which around half relate to force protection.
On August 29, 2012, Lance Corporal Stjepan Milosevic, Sapper James Martin and Private Robert Poate were killed in the attack.
A person wearing an Afghan National Army uniform opened fire with an automatic weapon inside a patrol base 20 kilometres north of Tarin Kowt in Oruzgan province.
Two other diggers were wounded.
The assailant was identified as Sergeant Hek Matullah, an Afghan National Army soldier.
He remains on the run.
Vice Chief of the Defence Force, Air Marshal Mark Binskin says the inquiry officer found only the minimum level of authorised protection was available to provide security for the soldiers.
Air Marshal Binskin said the inquiry officer found that having a single roving picket on duty at the base on the day was not adequate.
"He also found the decision to adopt a relaxed level of security - Australians were not in a state of readiness - was not in accordance with orders in place at the time," he said.
Some soldiers on the base were dressed in gym gear and not wearing their body armour.
"This limited their ability to react and was not in line with the usual existing standard operating procedures," Air Marshal Binskin said.
Two soldiers had since been disciplined over the pickets and inappropriate dress, he added.
"Although shortfalls in force protection were identified, the inquiry officer was not able to prove or disprove whether these arrangements directly or indirectly gave Hek Matullah the opportunity to attack Australian soldiers," Air Marshal Binskin said.
Intelligence had not highlighted a likely risk of insider attacks prior to the shooting, although Air Marshal Binskin said such threats were "complex and evolving".
"In terms of intelligence prior to this attack the inquiry officer found there was no intelligence available to Australia or (the) coalition to suggest there was a specific insider threat," he said.
Nor was there information that raised concerns about Hek Matullah.
"In fact, his existence was unremarkable from a personnel or intelligence perspective," Air Marshal Binskin said.
The inquiry officer found there was some truth in claims the Afghan National Army were aware of Hek Matullah's Taliban links, but that on this occasion he had acted independently.
"This is supported by the fact the Taliban has not claimed responsibility for the attack, as they normally do," Air Marshal Binskin said.
Air Marshal Binskin said the lesson for commanders on the ground is to provide the best level of protection possible for their forces.
"Don't take anything for granted," he said.
He said the company commander had been deeply affected by the deaths.
"Any commander who has deaths, whether it's in combat or in training, or on exercise, it hits you hard. You do take it personally," he said.
The patrol commander on duty at the time was one of three people named as having "a case to answer", based on the report, Air Marshal Binskin said.
It was he who had instructed a "minimum" level of force protection be in place at the time of the attack.
Air Marshal Binskin said that was not appropriate, but conceded greater security would not have necessarily prevented the deaths.
"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 although the base had sufficient resources to provide force protection, the decisions made weren't appropriate.
But 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 Hek Matullah was a threat to Australians," he said.
Defence has agreed to all six recommendations made by the inquiry officer.
Four recommendations relate to the possible administrative action against three ADF members, which the chief of the defence force has referred to the chief of army for consideration.
The fifth recommendation concerns instant response capability that has been implemented and the sixth is that a commission of inquiry is not warranted.
He said since the attack the Afghan National Army had continued to improve its recruitment screening process.
"This was a highly complex situation, our intelligence and resourcing were appropriate, however there were shortfalls in the force protection measures and in the decisions made on the ground," Air Marshal Binskin said.
Bringing Hek Matullah to justice remained a key focus.
"Let me assure you, we will not let this go."