Liberal frontbencher Christopher Pyne flagged the possibility of an onus of proof reversal on citizens returning from countries in civil war and said the government was "disgusted" with terrorists fighting overseas.
The changes would mean Australians returning from those countries would need to explain what they had been doing.
Prime Minister Tony Abbott refused to detail the changes, but said the government would do everything it reasonably could to stop jihadists returning.
"We do not want people who have been radicalised and militarised coming back to this country," Mr Abbott told reporters on Friday.
The government estimates about 60 Australians are fighting abroad, and several others have returned.
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Mr Pyne said the return of "murderous terrorists" involved in the "atrocities of Syria and Iraq" were a serious threat to security.
He said reversal of the onus of proof would likely come with a "risk" ranking system.
Those who had been "hanging out in country Syria" for several months would need to properly explain themselves.
The Australian Greens say the proposed changes could mean humanitarian workers and journalists would have to prove they are not criminals.
Greens senator Penny Wright said she was concerned the laws could permanently erode human rights.
The government introduced the first tranche of new anti-terrorism laws on July 16 and the second is expected to go to cabinet within weeks.
Arrest warrants have been issued for two Australians fighting for a banned terrorist group in Syria and Iraq.
