[word=a] [tag=JJ] [lemma=computer] □ □
[word=a] [tag=JJ] [lemma=computer] [□] □
[word=a] [tag=JJ] [lemma=computer] (□ | □) □
The programs can be written to perform malicious tasks after infecting a new computer , or do no more than copy themselves from machine to machine . The problem is that generating large NT rainbow tables is beyond the scale of a single computer , or even a hundred computers .