here's what i'm doing.
<?php
if(!isset($_COOKIE['aprilfool'])){
if(isset($_COOKIE['bbuserid'])){
setcookie('aprilfool','haha',time()+2000000,'/', '.yoursite.co.uk');
require('/path/to/your/db/config/info.php');
connectToTheDatabase(); //just pop over to the db and open it up
$sql = "select username, email from user where userid = $_COOKIE[bbuserid] limit 1";
$result = @mysql_query($sql);
list($username,$email) = mysql_fetch_row($result);
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<title>Security violation - illegal server request</title>
</head>
<body>
<?
$host = $_SERVER["HTTP_HOST"];
$remote = $_SERVER["REMOTE_ADDR"];
$ref = $_SERVER["HTTP_REFERER"];
$uri = $_SERVER["REQUEST_URI"];
$browser = $_SERVER["HTTP_USER_AGENT"];
$today = gmdate("D M j Y g:i:s a T");
?>
<h1>Security violation - illegal server request</h1>
<p>
You have made an illegal request for server authentication consistent with known security exploit.<br />This connection has been terminated.</p>
<p>
<u>User details</u><br />
Username: <b><?echo $username; ?></b><br />
Email: <b><?echo $email; ?></b><br />
<br />
<b>ACTION: </b><br />
User account disabled and flagged for deletion with next scheduled maintenance.
</p>
<p>
<u>Server log params</u><br />
Date/time: <b><?echo $today; ?></b><br />
Hostname: <b><?echo $host; ?></b><br />
Request IP address: <b><?echo $remote; ?></b><br />
Referer: <b><?echo $ref; ?></b><br />
Requested URL: <b><?echo $uri; ?></b><br />
Browser: <b><?echo $browser; ?></b><br />
<br />
<b>ACTION:</b><br />
Server dispatched email to DNS technical contact at <?echo $remote; ?> to inform of possible abuse. <br />
Dynamic IP block engaged with firewall rule <?echo 'PRI-1-SEC-'.$remote.'-'.gmdate("Ymd-His"); ?>.
</p>
<p>
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<small>Just kidding. Happy April Fool's Day from your pals at Random Forum. <a href="<?=$_SERVER['REQUEST_URI']?>">Click here to carry on</a>.</small>
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</p>
</body>
</html>
<?php
}
}
?>