Billboard Utilising Graffitists Against Unhealthy Promotions (BUGA-UP) started in 1979 in Australia. The movement aims at modifying billboard advertisement that promote unhealthy products. Mostly alcoholic beverages and tobacco product billboards were targeted and modified with graffiti.
It is interesting to see how their messages are buit on top of existing ones. The original advertisements were perhaps the results of thoughtful design process and marketing strategies, but the graffiti mocks the efforts and talks about the other side of the story. The use of spray cans add an element of covert human activity and therefore further contrasts with the original layout.
BUGA-UP website also has a how to page that provides instructions for creating custom tools and provides guidelines and suggestions on how to go ahead with graffiti. This has an appearance of procedural art practice.