Back when FreeCause ran the Dividend Miles mall there was a ‘toolbar’ you could download which would automatically cause you to earn US Airways miles when shopping at a participating merchant, and they also gave you a handful of miles for internet searches.
US Airways changed companies administering their mall, they now use Cartera Commerce which runs the American and Delta malls for instance.
Cartera has introduced a similar tool and they will give you 500 miles for downloading it and using it once (such as doing just one internet search with it). You can of course uninstall it afterward.
Here’s the FAQ for the StoreFront Assistant.