Here's what I've come up with so far. Basically I iterate over each packet and generate substrings from size 2 to the size of the packet. I then compare that against all of the other packets. It needs some tweaking in that area, but I get output that makes sense. Only problem is that on my machine, running it with large packets kills the OS after an hour or so. Apparently I need to make some memory optimizations somewhere. All comments are appreciated! Windows environ - no #! 
die "No file name" unless @ARGV;

my @packets = ();

while (<>)
{
 push(@packets,$_);
}
chop(@packets);

my $maxlen =0;
my $index = 0;
my $curpack;
my %all;

# iterate over all packets
foreach $curpack (@packets)
{
 $maxlen = length($curpack);

 # substring size
 for (my $fsize = 2; $fsize < $maxlen; $fsize ++)
 {
  # packet to compare against
  for (my $pnum = 0; $pnum < @packets; $pnum ++)
  {
   # start substr'ing at index 0
   for (0..$maxlen-$fsize)
   {
    # don't compare against self
    if ($index != $pnum)
    {
     my $str = substr($curpack,$_,$fsize);
     my @temparr = ($packets[$pnum] =~ /$str/g);
     my $nmatch = @temparr;
     if (defined($all{$str}))
     {
      $all{$str} += $nmatch;
     }
     else
     {
      $all{$str} = $nmatch;
     }
    undef @temparr;
    }
   }
  }
 }
 $index ++;

 # print results for current packet
 print "Comparing packet ",$index," to all others:\n";
 my $value;
 my @sort = sort {length($b) <=> length($a)} keys %all;
 foreach $value (@sort)
 {
  if ($all{$value} > 0)
  {
   print "$value: $all{$value} times\n";
  }
  delete($all{$value});
 }
 undef @sort;
}

exit;

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In reply to (Guildenstern) Re: Finding patterns (prelim code) by Guildenstern
in thread Finding patterns in packet data? by Guildenstern

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