diff --git a/inc/config.php b/inc/config.php
index a83edecd..092b1005 100644
--- a/inc/config.php
+++ b/inc/config.php
@@ -18,7 +18,8 @@
 		'cookies' => Array(),
 		'error' => Array(),
 		'dir' => Array(),
-		'mod' => Array()
+		'mod' => Array(),
+		'spam' => Array()
 	);
 	// Database stuff
 	
@@ -92,6 +93,7 @@
 	$config['error']['locked']			= 'Thread locked. You may not reply at this time.';
 	$config['error']['nopost']			= 'You didn\'t make a post.';
 	$config['error']['flood']			= 'Flood detected; Post discared.';
+	$config['error']['spam']			= 'Your request looks automated; Post discared.';
 	$config['error']['unoriginal']		= 'Unoriginal content!';
 	$config['error']['muted']			= 'Unoriginal content! You have been muted for %d seconds.';
 	$config['error']['youaremuted']		= 'You are muted! Expires in %d seconds.';
@@ -282,6 +284,36 @@
 	$config['mod']['link_lock'] = '[Lock]';
 	$config['mod']['link_unlock'] = '[-Lock]';
 	
+	// Spam filter
+	$config['spam']['hidden_inputs_min']	= 4;
+	$config['spam']['hidden_inputs_max']	= 12;
+	// These are fields used to confuse the bots. Make sure they aren't actually used by Tinyboard, or it won't work.
+	$config['spam']['hidden_input_names'] = Array(
+		'user',
+		'username',
+		'login',
+		'search',
+		'q',
+		'url',
+		'firstname',
+		'lastname',
+		'text',
+		'message'
+	);
+	// Always update this when adding new valid fields to the post form, or EVERYTHING WILL BE DETECTED AS SPAM!
+	$config['spam']['valid_inputs'] = Array(
+		'hash',
+		'board',
+		'thread',
+		'mod',
+		'name',
+		'email',
+		'subject',
+		'post',
+		'body',
+		'password'
+	);
+	
 	// A small file in the main directory indicating that the script has been ran and the board(s) have been generated.
 	// This keeps the script from querying the database and causing strain when not needed.
 	$config['has_installed'] = '.installed';
diff --git a/inc/functions.php b/inc/functions.php
index 854b0397..8b6ac65a 100644
--- a/inc/functions.php
+++ b/inc/functions.php
@@ -634,6 +634,105 @@
 		}
 	}
 	
+	function createHiddenInputs() {
+		global $config;
+		
+		$inputs = Array();
+		
+		shuffle($config['spam']['hidden_input_names']);
+		$hidden_input_names_x = 0;
+		
+		$input_count = rand($config['spam']['hidden_inputs_min'], $config['spam']['hidden_inputs_max']);
+		for($x=0;$x<$input_count;$x++) {
+			if(rand(0, 2) == 0 || $hidden_input_names_x < 0) {
+				// Use an obscure name
+				$name = substr(base64_encode(sha1(rand())), 0, rand(2, 40));
+			} else {
+				// Use a pre-defined confusing name
+				$name = $config['spam']['hidden_input_names'][$hidden_input_names_x++];
+				if($hidden_input_names_x > count($config['spam']['hidden_input_names']))
+					$hidden_input_names_x = -1;
+			}
+			
+			if(rand(0, 2) == 0) {
+				// Value must be null
+				$inputs[$name] = '';
+			} elseif(rand(0, 4) == 0) {
+				// Numeric value
+				$inputs[$name] = rand(0, 100);
+			} else {
+				// Obscure value
+				$inputs[$name] = substr(base64_encode(sha1(rand())), 0, rand(2, 40));
+			}
+		}
+		
+		$content = '';
+		foreach($inputs as $name => $value) {
+			$content .= '<input type="hidden" name="' . htmlspecialchars($name) . '" value="' . htmlspecialchars($value) . '" />' . "\n	";
+		}
+		
+		// Create a hash to validate it after
+		// This is the tricky part.
+		
+		// First, sort the keys in alphabetical order (A-Z)
+		ksort($inputs);
+		
+		$hash = '';
+		
+		// Iterate through each input
+		foreach($inputs as $name => $value) {
+			$hash .= $name . '=' . $value;
+		}
+		
+		// Add a salt to the hash
+		$hash .= $config['cookies']['salt'];
+		
+		// Use SHA1 for the hash
+		$hash = sha1($hash);
+		
+		// Append it to the HTML
+		$content .= '<input type="hidden" name="hash" value="' . $hash . '" />';
+		
+		return $content;
+	}
+	
+	function checkSpam() {
+		global $config;
+		
+		if(!isset($_POST['hash']))
+			return true;
+		
+		$hash = $_POST['hash'];
+		
+		// Reconsturct the $inputs array
+		$inputs = Array();
+		
+		foreach($_POST as $name => $value) {
+			if(in_array($name, $config['spam']['valid_inputs']))
+				continue;
+			
+			$inputs[$name] = $value;
+		}
+		
+		// Sort the inputs in alphabetical order (A-Z)
+		ksort($inputs);
+		
+		$_hash = '';
+		
+		// Iterate through each input
+		foreach($inputs as $name => $value) {
+			$_hash .= $name . '=' . $value;
+		}
+		
+		// Add a salt to the hash
+		$_hash .= $config['cookies']['salt'];
+		
+		// Use SHA1 for the hash
+		$_hash = sha1($_hash);
+		
+		return $hash != $_hash;
+	}
+	
 	function buildIndex() {
 		global $board, $config;
 		sql_open();
@@ -648,6 +747,7 @@
 			$content['pages'] = $pages;
 			$content['pages'][$page-1]['selected'] = true;
 			$content['btn'] = getPageButtons($content['pages']);
+			$content['hidden_inputs'] = createHiddenInputs();
 			@file_put_contents($filename, Element('index.html', $content)) or error("Couldn't write to file.");
 			
 			if(isset($md5) && $md5 == md5_file($filename)) {
@@ -837,6 +937,7 @@
 			'index' => $config['root'],
 			'id' => $id,
 			'mod' => $mod,
+			'hidden_inputs' => $content['hidden_inputs'] = createHiddenInputs(),
 			'return' => ($mod ? '?' . $board['url'] . $config['file_index'] : $config['root'] . $board['uri'] . '/' . $config['file_index'])
 		));
 			
diff --git a/mod.php b/mod.php
index 034e18a8..86ae4b5d 100644
--- a/mod.php
+++ b/mod.php
@@ -327,6 +327,7 @@
 			$page['pages'] = getPages(true);
 			$page['pages'][$page_no-1]['selected'] = true;
 			$page['btn'] = getPageButtons($page['pages'], true);
+			$page['hidden_inputs'] = createHiddenInputs();
 			$page['mod'] = true;
 			
 			echo Element('index.html', $page);
diff --git a/templates/index.html b/templates/index.html
index 59ce3f54..f75b9015 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -13,6 +13,7 @@
 	
 	
 	<form onsubmit="return dopost(this);" enctype="multipart/form-data" action="{post_url}" method="post">
+	{hidden_inputs}
 	<input type="hidden" name="board" value="{board[uri]}" />
 	{mod?<input type="hidden" name="mod" value="1" />}
 		<table>
diff --git a/templates/thread.html b/templates/thread.html
index 19434be3..eae22720 100644
--- a/templates/thread.html
+++ b/templates/thread.html
@@ -12,7 +12,7 @@
 	<div class="title">{board[title]?{board[title]}}<p>{mod?<a href="?/">Return to dashboard</a>}</p></div>
 	
 	<div class="banner">Posting mode: Reply <a class="unimportant" href="{return}">[Return.]</a></div>
-	<form onsubmit="return dopost(this);" enctype="multipart/form-data" action="{post_url}" method="post">
+	<form onsubmit="return dopost(this);" enctype="multipart/form-data" action="{post_url}" method="post">{hidden_inputs}
 	<input type="hidden" name="thread" value="{id}" />
 	<input type="hidden" name="board" value="{board[uri]}" />
 	{mod?<input type="hidden" name="mod" value="1" />}