Simple anti-spam mechanism

inc/config.php

@@ -303,7 +303,14 @@
 		'json_response',
 		'user_flag',
 		'no_country',
-		'tag'
+		'tag',
+		'simple_spam'
+	);
+
+	// Enable simple anti-spam measure.
+	$config['simple_spam'] = array (
+		'question' => 'What is 2 + 2?',
+		'answer' => '4'
 	);
 
 	// Enable reCaptcha to make spam even harder. Rarely necessary.
@@ -1158,6 +1165,7 @@
 	$config['error']['flood']		= _('Flood detected; Post discarded.');
 	$config['error']['too_many_threads']	= _('The hourly thread limit has been reached. Please post in an existing thread.');
 	$config['error']['spam']		= _('Your request looks automated; Post discarded.');
+	$config['error']['simple_spam']        = _('You must answer the question to make a new thread. See the last field.');
 	$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.');

post.php

@@ -558,6 +558,11 @@ if (isset($_POST['delete'])) {
 
 
 	if (!$dropped_post) {
+		if (isset($config['simple_spam']) && $config['simple_spam'] && $post['op']) {
+			if (!isset($_POST['simple_spam']) || $config['simple_spam']['answer'] != $_POST['simple_spam']) {
+				error($config['error']['simple_spam']);
+			}
+		}
 
 		// Check if banned
 		checkBan($board['uri']);

templates/post_form.html

@@ -215,6 +215,16 @@
 				{{ antibot.html() }}
 			</td>
 		</tr>{% endif %}
+		{% if config.simple_spam and not id %}<tr>
+			<th>
+				{{ config.simple_spam.prompt }}
+				{{ antibot.html() }}
+			</th>
+			<td>
+				<input type="text" name="simple_spam" value="" size="12" maxlength="18" autocomplete="off"> 
+				{{ antibot.html() }}
+			</td>
+		</tr>{% endif %}
 	</table>
 {{ antibot.html(true) }}
 <input type="hidden" name="hash" value="{{ antibot.hash() }}">