IBM Big Blue is the chess program that defeated the grandmaster Gary Kasprov in 1997. This was a shock at the time as chess at grandmaster was considered too difficult for a computer. Deep Blue made extensive use of 'brute force' lookahead running on an IBM supercomputer and Kasprov labelled it an 'alien opponent' as it played in a very different way to a human.
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See also alien intelligence
Links:
Wikipedia: Deep Blue (chess computer)- scientificamerican.com: Scientific American: 20 Years after Deep Blue: How AI Has Advanced Since Conquering Chess