Mostly found with:
for i in nselib/*.lua scripts/*.nse; do
echo $(perl -lne 'BEGIN{$a=$p=0}next unless $_;/^(\s*)/;' \
-e '$l=length$1;next if$l==$p;$a+=(abs($l-$p)-$a)/$.;' \
-e '$p=$l;END{print$a}' $i) $i
done | sort -nr
And indented with: https://gist.github.com/bonsaiviking/8845871
whois-ip.nse was particularly mangled (probably my fault due to using
vim's built-in indentation script, but it could be structured better)
assigned to this backdoor.
Added a final 'exit' command to terminate the remote '/bin/sh', however I don't
think that this is necessary since the backdoor was very simple: it did not
fork(), and closing the stdin of the '/bin/sh' will terminate it.