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Old 05-19-2016, 12:12 PM   #1
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What does this command do ? Malicious code ?

Hi everyone

Total Linux newbie (experimenting with Synology Disk Station Manager NAS operation system, excuse me a million times if I'm sooo newbie that I'm wrong that DSM is a type of Linux)

Found on the NAS a well-hidden user downloaded file called "" which contains the following:

threads=4; for crf in 20 21; do db=-1:-1; for tune in "" "-tune grain" "-tune film"; do for f in S01/The.Twilight.Zone.S01E01*.mkv; do avconv -i "$f" -threads "$threads" -codec copy -c:v libx264 -preset placebo $tune -me_range 32 -me_method tesa -flags2 -fastpskip -subq 10 -g 1500 -bf 16 -b_strategy 2 -b-pyramid 2 -mixed-refs 1 -psy 1 -8x8dct 1 -partitions all -direct-pred auto -weightb 1 -deblock "$db" -crf "$crf" -frames $[5*60*24] /tmp/RE/"$f"-"$crf"-"$tune".mkv; echo; done; done; done

Could anyone explain what this does ?

As far as I know the ".sh" extension is the equivalent of an executable file in Windows (.bat/.exe/.com) ?

So is this a malicious file in a download targeting NAS users specifically ? That would be something I never saw before.

Thank you very much for any insight.

Old 05-19-2016, 12:39 PM   #2
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Hi Welcome to LQ.

I don't think it's malicious to the effect that it tries to do something other than be an annoyance. My read is that it will play a movie accompanied by sound to the Twilight Zone tune. Still I would recommend against running it.
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Old 05-19-2016, 02:24 PM   #3
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I would rather say it tries to convert a set of video files. Probably it was used once to do that and just not removed.
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