Deakin University counter-terrorism expert Greg Barton said Australians needed to put the Isis propaganda into perspective and "not succumb to the hype".
He described it as more a "hopeful Hail Mary gesture" than a real threat.
"If we had (intelligence of) internal communications that were mentioning places like Bankstown ... then you'd start to worry something was afoot," he told ABC radio. "It's not a specific threat. It's not a game changer."
Keenan said Isis, which is under pressure in Syria and Iraq, had an effective propaganda machine to spread its message in western countries.
"Australia is not going to be immune from that," he said.
But changes to counter-terrorism laws give police and intelligence agencies more powers to intervene earlier if they were concerned about the possibility of attacks.
Prime Minister Malcolm Turnbull, who is attending a meeting of south-east Asian leaders in Laos, said the Isis call highlighted the necessity for strong regional co-operation on security.
"Sharing of intelligence is more important than ever before," he told reporters. "But we do have to be very alert to the actions of these lone actors - individuals who ...for a variety of reasons, may be radicalised."
- AAP