See my and Tim's earlier posts. An order is at the discretion of the judge.
UNIFORM CIVIL PROCEDURE RULES 2005 - REG 42.21
(1A) In determining whether it is appropriate to make an order that a plaintiff referred to in subrule (1) give security for costs, the court may have regard to the following matters and such other matters as it considers relevant--
(a) the prospects of success or merits of the proceedings,
(b) the genuineness of the proceedings,
(c) the impecuniosity of the plaintiff,
(d) whether the plaintiff's impecuniosity is attributable to the defendant's conduct,
(e) whether the plaintiff is effectively in the position of a defendant,
(f) whether an order for security for costs would stifle the proceedings,
(g) whether the proceedings involves a matter of public importance,
(h) whether there has been an admission or payment in court,
(i) whether delay by the plaintiff in commencing the proceedings has prejudiced the defendant,
(j) the costs of the proceedings,
(k) whether the security sought is proportionate to the importance and complexity of the subject matter in dispute,
(l) the timing of the application for security for costs,
(m) whether an order for costs made against the plaintiff would be enforceable within Australia,
(n) the ease and convenience or otherwise of enforcing a New South Wales court judgment or order in the country of a non-resident plaintiff.
(1B) If the plaintiff is a natural person, an order for security for costs cannot be made merely on account of his or her impecuniosity.