Well it's not really a sci-fi blockbuster, it's really supposed to be more of a character study of the man and what happens around him. Even with the original book the aliens really just exist as a force of nature to change the lives of the characters so we can see how they cope, so really at the end they just need a quick and easy way to finish it off. Still it makes more sense as a Deus Ex Machina than uploading a pc virus to a totally alien computer system (coughID4
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