Three men were found guilty of planning to conduct a terror attack in Melbourne's CBD over the Christmas period in 2016, in a verdict handed down earlier this month, the ABC can reveal.

Abdullah Chaarani, 27, Ahmed Mohamed, 25, and Hamza Abbas, 23, face a possible sentence of life imprisonment for their roles in the plot.

The jury took just over six days to deliver their verdict on November 2, after a lengthy trial that heard the men had purchased machetes as well as metal pipes, light globes and batteries to make explosives, and had tried to obtain guns.

They had also conducted reconnaissance at Federation Square and in the surrounding area, where the prosecution alleged they wanted to carry out an attack in order to maximise casualties.

The men were unaware they were being followed and monitored by police.

A series of telephone messages, emails and texts between the men were intercepted by authorities. Some of them detailed support for the Islamic State group and discussed their perceived obligation to join jihad.

The guilty verdict was initially subject to a non-publication order after an application to keep it secret was made by the men's defence lawyers.

Supreme Court Justice Christopher Beale denied that request, but suppressed the verdict to allow them time to appeal his decision in a higher court.

The appeal judges rejected the application to have the verdict suppressed.

The reasons for the suppression order cannot be reported.

The prosecution said the men targeted Federation Square to maximise casualties. ( ABC Radio Melbourne: Simon Leo Brown )

Hamza Abbas's brother Ibrahim Abbas was the key witness in the case.

The 24-year-old claimed to have been the group's ringleader and told the jury he had convinced his three co-accused to take part in the Islamic State-inspired plot.

Ibrahim Abbas told police he was thinking through the attack when the men were filmed on CCTV at Federation Square in the days before their arrest.

"I'm just thinking about how I'm going to use my knife as efficiently as possible," he told police in an interview played to the jury.

"I was going to run at them, slice their necks."

Ibrahim Abbas said he had told the men "it's not hard to kill a person with a machete, it just takes one slice to the neck".

The court was told Abbas had planned to put an explosive vest on his brother Hamza.

The men followed an extreme brand of Sunni Islam that directed followers to wage war against non-believers and believed they would be sent to paradise as martyrs, the jury was told.

At the time of their arrests, then-prime minister Malcolm Turnbull called the plot "one of the most substantial terrorist plots that have been disrupted over the last several years".

During the men's trial, the prosecution detailed the steps the men took to plan the attack.

In early October, both Mohamed and Chaarani conducted internet research on how to make improvised explosive devices (IEDs), including accessing an article about bombmaking in an Al Qaeda publication.

They made two trips to Bunnings in Broadmeadows, in Melbourne's north, in November and December to purchase supplies.

In December, the three men bought more supplies from Chemist Warehouse in Broadmeadows while two of them went to the outdoor store Boating, Camping and Fishing in Coburg and bought machetes.

They attempted to make an explosive compound, while Chaarani tried to get a firearms licence by saying he wanted to hunt feral animals on Crown land.