When I first heard this song, I thought it was an awesome mashup of M.I.A. and the clash. But it's not a mashup, this song is on her awesome album. In this video, two of beastie boys make a cameo, see if you can spot them.
I eventually listened to the Clash song "Straight to Hell" and the M.I.A. "PAPER PLANES" back to back, and realized that they did not sample the Clash, but covered the riff, so it's like a cover-sample.
Here is the original Clash song:
Now you can play them back to back in the comfort of your home or office.