Wednesday, January 16, 2008

Proxy Detector

* Proxy Detector v0.1
* copyrights by: Daantje Eeltink (
* first build: Mon Sep 18 21:43:48 CEST 2006
* last build: Tue Sep 19 10:37:12 CEST 2006
* Description:
* This class can detect if a visitor uses a proxy server by scanning the
* headers returned by the user client. When the user uses a proxy server,
* most of the proxy servers alter the header. The header is returned to
* PHP in the array $_SERVER.
* License:
* GPL v2 licence. (
* Support:
* If you like this class and find it usefull, please donate one or two
* coins to my PayPal account
* Todo:
* Add open proxy black list scan.

class proxy_detector {

* Set defaults...
function proxy_detector(){
$this->config = array();
$this->lastLog = "";

//set default headers
$this->scan_headers = array(

* VOID setHeader( STRING $trigger )
* Set new header trigger...
function setHeader($trigger){
$this->scan_headers[] = $trigger;

* ARRAY $triggers = getHeaders( VOID )
* Get all triggers in one array
function getHeaders(){
return $this->scan_headers;

* VOID setConfig( STRING $key, STRING $value)
* Set config line...
function setConfig($key,$value){
$this->config[$key] = $value;

* MIXED $config = getConfig( [STRING $key] )
* Get all config in one array, or only one config value as a string.
function getConfig($key=''){
return $this->config[$key];
return $this->config;

* STRING $log = getLog( VOID )
* Get last logged information. Only works AFTER calling detect()!
function getLog(){
return $this->lastLog;

* BOOL $proxy = detect( VOID )
* Start detection and return true if a proxy server is detected...
function detect(){
$log = "";

//scan all headers
foreach($this->scan_headers as $i){
//proxy detected? lets log...
$log.= "trigger $i: ".$_SERVER[$i]."\n";

//let's do something...
$log = $this->lastLog = date("Y-m-d H:i:s")
."\nDetected proxy server: "
.gethostbyaddr($_SERVER['REMOTE_ADDR'])." ({$_SERVER['REMOTE_ADDR']})\n".$log;

//mail message
Proxy detected at {$_SERVER['REQUEST_URI']}",$log);

//write to file
$f = $this->getConfig('LOG_FILE');
$fp = fopen($f,'a');
die("<strong>Fatal Error:</strong> Couldn't write to file:
Please check if the path exists and is writable for the webserver or php...");

return true;

//nope, no proxy was logged...
return false;


Browsing the code you will notice that it uses a log file to store the data so we will have to create one called "
proxy_detector.log". Don't forget to give it the proper permission on the server (CHMOD it to make it writable).

Ok so we already have 2 files. Let's go ahead and create a new one called ""
.This one will initiate our class for our future use and do what we want it to do so I suggest you to edit it to suit your needs. Copy paste this code and save it:

* Proxy Detector v0.1
* Implementation example.
* Mon Sep 18 23:29:47 CEST 2006
* by:
* Documentation:
* I use this file as an include at the top of some php files
* to block proxy users from the scripts that included this file.
* This file is only an example on how to implement the detector class.
* But it could be usefull as is...
* Check the remarks in the class for more documentation.

//include detector class, assuming it's in the same directory as this file...

//init class
$proxy = new proxy_detector();

//set optional extra triggers, no need to...
//I think I've got all of them covered in the class...
// $proxy->setTrigger('HTTP_SOME_HEADER_1');
// $proxy->setTrigger('HTTP_SOME_HEADER_2');

//set optional config
// $proxy->setConfig('MAIL_ALERT_TO','');
// $proxy->setConfig('LOG_FILE','/home/daantje/public_html/proxy/proxy_detector.log');

//start detect

//returned true, lets die...
echo "<h1>Proxy detected</h1>";
echo "
Please disable your proxy server in your browser preferences or internet settings,
and try again.<br><br>";

//parse logged info
echo nl2br($proxy->getLog());

//some credits...
echo "<hr><strong>proxy detector v0.1</strong>
- &copy;2006 < a href=\"\"

//and do nothing anymore! (but not in my example)

//else, proceed as normal, put your code here...

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