A former junior Defence bureaucrat has been jailed for uploading secret information online.
But Australia's former army chief, Peter Leahy, says Michael Scerba should have been locked up for longer for his "self-indulgent and selfish" security breach.
Justice Richard Refshauge on Thursday sentenced Scerba, 24, to one year jail for disclosing secret information.
Scerba will serve three months behind bars, with the remainder of the sentence suspended upon signing a good behaviour order and a $500 security bond.
He will be released in February.
Scerba pleaded guilty in the ACT Supreme Court to posting a secret Defence Intelligence Organisation report to image sharing website 4chan in October 2012.
Scerba, then a 21-year-old Department of Defence graduate, downloaded the secret 15-page document from Secret Defence Security Network, burnt it to a disc, took it home, and posted the first two pages to the online forum.
The first image he posted included the comment "Julian Assange is my hero".The post was discovered and Scerba's home raided by Australian Federal Police. Forensic tests of his computer and a broken disc located in his bin confirmed his involvement.
The contents of the leaked report are the subject of strict secrecy provisions, but the court on Thursday heard the posts revealed the identity of intelligence sources, gathering methods, and classified aspects of strategic partnerships between Australia and foreign countries.
The document was meant for the "Five Eyes" intelligence alliance involving Australia and its top allies.
Scerba possessed a secret, or negative vetting level one, clearance, and had been with the department for about eight months at the time.
The court heard the post disappeared after about one hour and at least 12 people had viewed and commented on it in that time. But it was unknown the total number who had accessed the sensitive information. The court also heard one 4chan user had downloaded and reposted the image.
In handing down the sentence, Justice Refshauge accepted that Scerba had not intended to compromise national security, although he knew the disclosure could cause harm.
"The level of harm may never be known," the judge said.
The court heard Scerba had no prior convictions and had been assessed as a low risk of reoffending. He had accepted responsibility and acknowledged the breach of trust, but had minimised his actions.
Justice Refshauge said he had shown limited remorse and was yet to fully recognise the full consequences of his crime. The judge accepted Scerba's mental health had impaired his judgment, but found he knew what he was doing.
He said Scerba had displayed a level of planning and detail, and attempted to avoid detection.
Justice Refshauge also accepted there had been no political, ideological, or financial motive for the offending. He found the seriousness of the offence required a sentence of full time imprisonment.
Now retired Lieutenant General Peter Leahy, who was chief of army between 2002 and 2008, said he thought the jail sentence was a "good thing".
But he believed the three months Scerba will spend behind bars had been too lenient.
"I'm pleased to see the court has imprisoned him, although I think a three month prison term is inadequate, but at least they are reinforcing the laws of the Commonwealth," Professor Leahy, now the director of the University of Canberra's National Security Institute, said.
"I think there's an attitude among too many these days that they can, for personal reasons, breach security protocols ... [and it] is reinforced by the leniency of the courts.
"[The jail sentence] sends a message to people who think they can breach Commonwealth security, and I think they should listen carefully to the message."
CORRECTION: An earlier version of this story said Justice Richard Refshauge had found there had been political, ideological, or financial motive for the offending. Instead, the judge found Scerba had none of those motives.