XXXX (pronounced fourex) is a beer brewed in Brisbane, Australia by Castlemaine Perkins(now owned by Lion Nathan). It can be recognised by its distinctive yellow and gold label showing four large X's. First brewed in 1916 it is described by its makers as:

"A traditional Australian lager with a clean, crisp taste and a satisfying after-bitterness. XXXX Bitter's delicate aroma comes from the blending of two hop varieties and a sweeter, fruity tang from the yeast. High drinkability in warm climates"

It has nothing to do with porn. Indications that XXXX is your preferred beer makes you a Queenslander. Other people like VB (Victoria Bitter).