Index: t3lib/config_default.php
===================================================================
--- t3lib/config_default.php	(Revision 3069)
+++ t3lib/config_default.php	(Arbeitskopie)
@@ -88,6 +88,8 @@
 		'systemLogLevel' => 0,					// Integer: Only messages with same or higher severity are logged; 0 is info, 1 is notice, 2 is warning, 3 is error, 4 is fatal error.
 		'maxFileNameLength' => 60,				// Integer, This is the maximum file name length. The value will be taken into account by basic file operations like renaming or creation of files and folders.
 		'UTF8filesystem' => 0,					// Boolean: If true and [BE][forceCharset] is set to utf-8, then TYPO3 uses utf-8 to store file names. This allows for accented Latin letters as well as any other non-latin characters like Cyrillic and Chinese.
+		'proxyFixClientAddress' => false,			// Boolean: If it appears like all client requests come from the same host, then this is probably because there is a proxy between the server and the clients. If this setting is enabled, TYPO3 sends the HTTP_X_FORWARDED_FOR header instead of REMOTE_ADDR and REMOTE_HOST, as some proxy servers serve the original IP in this field instead. WARNING: Do not use this unless you are sure that your requests come from such a proxy. Otherwise, the field could easily be faked, which is a problem when it comes to security check...
+
 	),
 	'EXT' => Array (	// Options related to the Extension Management
 		'noEdit' => 1,							// Boolean: If set, the Extension Manager does NOT allow extension files to be edited! (Otherwise both local and global extensions can be edited.)
Index: t3lib/class.t3lib_div.php
===================================================================
--- t3lib/class.t3lib_div.php	(Revision 3069)
+++ t3lib/class.t3lib_div.php	(Arbeitskopie)
@@ -3193,9 +3193,16 @@
 					$retVal = $_SERVER['PATH_INFO'];
 				}
 			break;
-				// These are let through without modification
+				// Deal with some proxy servers that hide the clients IP address/hostname
 			case 'REMOTE_ADDR':
 			case 'REMOTE_HOST':
+				if ($GLOBALS['TYPO3_CONF_VARS']['SYS']['proxyFixClientAddress']) {	// This is for proxy servers that send their own IP instead of the original REMOTE_HOST value. Instead, the remote host is stored in HTTP_X_FORWARDED_FOR.
+					$retVal = (isset($_SERVER['HTTP_X_FORWARDED_FOR']) && strlen($_SERVER['HTTP_X_FORWARDED_FOR'])) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : $_SERVER[$getEnvName];
+				} else {
+					$retVal = $_SERVER[$getEnvName];
+				}
+			break;
+				// These are let through without modification
 			case 'HTTP_REFERER':
 			case 'HTTP_HOST':
 			case 'HTTP_USER_AGENT':