Anti virus program anser kryptrings script som skadeligt?

Hey!

Jeg under mig lidt over hvorfor dette kryptrings script anses som skadeligt for de fleste virus programmer?

<?PHP
function _fwk_filter_encrypt($content)
{ 
  $table = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_@";
  $xor = 165;
  $table = array_keys(count_chars($table, 1));
  $i_min = min($table);
  $i_max = max($table);
  for ($c = count($table); $c > 0; $r = mt_rand(0, $c--))
    array_splice($table, $r, $c - $r, array_reverse(array_slice($table, $r, $c - $r)));
   
  $len = strlen($content);
  $word = $shift = 0;
  for ($i = 0; $i < $len; $i++)
  { 
    $ch = $xor ^ ord($content[$i]);
    $word |= ($ch << $shift);
    $shift = ($shift + 2) % 6;
    $enc .= chr($table[$word & 0x3F]);
    $word >>= 6;
    if (!$shift)
    {
      $enc .= chr($table[$word]);
      $word >>= 6;
    }
  }
  if ($shift)
    $enc .= chr($table[$word]);

  $tbl = array_fill($i_min, $i_max - $i_min + 1, 0);
  while (list($k,$v) = each($table))
    $tbl[$v] = $k;
  $tbl = implode(",", $tbl);
 
  $fi = ",p=0,s=0,w=0,t=Array({$tbl})";
  $f  = "w|=(t[x.charCodeAt(p++)-{$i_min}])<<s;";
  $f .= "if(s){r+=String.fromCharCode({$xor}^w&255);w>>=8;s-=2}else{s=6}";
 
  $r = "<script language=JavaScript>";
  $r.= "function decrypt_p(x){";
  $r.= "var l=x.length,b=1024,i,j,r{$fi};";
  $r.= "for(j=Math.ceil(l/b);j>0;j--){r='';for(i=Math.min(l,b);i>0;i--,l--){{$f}}document.write(r)}";
  $r.= "}decrypt_p(\"{$enc}\")";
  $r.= "</script>";
  return $r;
}
ob_start("_fwk_filter_encrypt");
?>

- Og i så fald, skulle der sidde nogle eksperter som kender en løsning på dette?