Biological contamination from space samples is a remote but accepted possibility. Signals received by searches for extraterrestrial intelligence (SETI) could also contain harmful information in the spirit of a computer virus, the so-called "SETI Hacker" hypothesis. Over the last four decades extraterrestrial intelligence searches have given little consideration to this possibility.
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Generally I would agree with you (Independence Day was on TV a few days ago), but this discussion about alien computer viruses is in a serious article...