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Keyword-based search blocking

If your search logs are full of spam with repeating keywords, you’re being targeted by a spammer. Their goal is to get visibility to their malicious URLs, hoping Google will index your search results pages with their spam URL in it.

There are probably better ways to stop these kinds of spammers, but here’s one approach you can use without any access to the server level settings. Add the following code to the theme functions.php:

add_filter( 'pre_get_posts', 'rlv_block_search' );
function rlv_block_search( $query ) {
    if (!empty($query->query_vars['s'])) {
        $blacklist = array( '大奖', 'q82' ); // add blacklist entries here; no need for whole words, use the smallest part you can
        foreach( $blacklist as $term ) {
            if( mb_stripos( $query->query_vars['s'], $term ) !== false ) exit();
        }
     }
}

Now any searches that include the blacklisted terms stops WordPress execution immediately. Be careful and only list things in black list that are never good searches. Parts of spammer URLs and for example Chinese characters on a site with no Chinese content are fairly safe bets. You can find your personal problem search terms from the site search logs.