Which of the following laws or acts, formed in Australia, enforces prohibition against cyber stalking?

The Stalking by Electronic Communications Act (2001) is not an Australian law - it is associated with Irish legislation targeting electronic harassment.

The Malicious Communications Act (1998) is a United Kingdom law that covers sending offensive or threatening messages, not Australian legislation.

Anti-Cyber-Stalking law (1999) is not an Australian act - various U.S. states enacted anti-cyberstalking statutes around this period, but this specific name does not correspond to Australian law.

The Stalking Amendment Act 1999 is Australian legislation that amended pre-existing stalking laws to include electronic forms of stalking, making it one of the earliest legal frameworks in Australia to address cyberstalking as a criminal offense. It expanded the definition of stalking to encompass conduct carried out via telephone, email, and internet communications. This act directly enforces prohibitions against cyber stalking within the Australian legal jurisdiction.