The Crimes Act 1958 (Vic) offence of stalking was originally intended to give more force to the Crimes (Family Violence) Act 1987 (Vic). However, given the wide definition of stalking in section 21A(2) of the Crimes Act, the offence of stalking has the potential to be applied to protest situations. Stalking includes following, telephoning, or giving offensive material to someone where there is the intention of causing physical or mental harm and the course of conduct engaged in actually did have that result. The penalty for this offence is up to 10 years jail.
Burglary is the offence of trespassing on property with criminal intent (ie. to commit an offence such as theft or assault). This could be used where protestors enter private property with the deliberate intention to damage it. The penalty is up to 10 years imprisonment (or 15 years for an "aggravated burglary" where the person was reckless as to whether a person was present at the time of entering the property).
There are a number of different charges of assault, each with a different penalty range, depending on how the assault occurred, whether a weapon was used and the injuries caused. Summary and indictable (more serious) assault or causing injury charges all carry significant maximum penalties, including terms of imprisonment.