WordPress « Pingback » DDoS attacks can generate a lot of requests to your website that can affect performances and availability.  You can recognize easily this attacks : you just need to do a tail -f  on your logs and you’ll probably see thousand of request that have a User-Agent « WordPress xxxx » on it. I don’t think bots are really interested by your website…
 
You can use rules in your .htaccess to block the user User-Agent but the best method for stopping it without charging your webserver is to use iptables :

iptables -N Wpddosblock
iptables -I INPUT -p tcp --dport 80 -m string --to 70 --algo bm --string 'GET /' -j Wpddosblock
iptables -A Wpddosblock -p tcp --dport 80 -m string --to 80 --algo bm ! --string 'User-Agent: WordPress/' -j RETURN
iptables -A Wpddosblock -p tcp --dport 80 -m string --to 300 --algo bm --string 'verifying pingback from' -j DROP
iptables -A Wpddosblock -j RETURN

You can also directly download my shellscript that do this for you here : wpddosblock.sh

You can do directly on your server :

wget --no-check-certificate https://www.christophe-casalegno.com/tools/wpddosblock.sh
chmod +x wpddosblock.sh
./wpddosblock.sh

You can use :

Order Deny,Allow
SetEnvIf User-Agent WordPress keep_out
Deny from env=keep_out

or

RewriteEngine on
RewriteCond %{HTTP_USER_AGENT} WordPress
RewriteRule .* - [F]

Christophe Casalegno
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