This can work if you are on an Apache hosting, and your provider allows you to edit the .htaccess file.

I use this rules on my static web sites, though taking out the lines:

### Real wp-comments-post.php - Denies any POST attempt made to a non-existing wp-comments-post.php ###
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /.*/wp-comments-post\.php.*\ HTTP/ [NC]
RewriteRule .* - [F,NS,L]

### HTTP PROTOCOL - Denies any badly formed HTTP PROTOCOL in the request, 0.9, 1.0, and 1.1 only ###
RewriteCond %{THE_REQUEST} !^[A-Z]{3,9}\ .+\ HTTP/(0\.9|1\.0|1\.1) [NC]
RewriteRule .* - [F,NS,L]

### BAD Content Length - Denies any POST request that doesnt have a Content-Length Header ###
RewriteCond %{REQUEST_METHOD} =POST
RewriteCond %{HTTP:Content-Length} ^$
RewriteCond %{REQUEST_URI} !^/(wp-admin/|wp-content/plugins/|wp-includes/).* [NC]
RewriteRule .* - [F,NS,L]

### BAD Content Type - Denies any POST request with a content type other than application/x-www-form-urlencoded|multipart/form-data ###
RewriteCond %{REQUEST_METHOD} =POST
RewriteCond %{HTTP:Content-Type} !^(application/x-www-form-urlencoded|multipart/form-data.*(boundary.*)?)$ [NC]
RewriteCond %{REQUEST_URI} !^/(wp-login.php|wp-admin/|wp-content/plugins/|wp-includes/).* [NC]
RewriteRule .* - [F,NS,L]

### NO HOST - Denies requests that dont contain a HTTP HOST Header ###
RewriteCond %{REQUEST_URI} !^/(wp-login.php|wp-admin/|wp-content/plugins/|wp-includes/).* [NC]
RewriteCond %{HTTP_HOST} ^$
RewriteRule .* - [F,NS,L]

### Bogus Graphics Exploit - Denies obvious exploit using bogus graphics ###
RewriteCond %{HTTP:Content-Disposition} \.php [NC]
RewriteCond %{HTTP:Content-Type} image/.+ [NC]
RewriteRule .* - [F,NS,L]

### This also will catch a lot of spammers ###
RewriteCond %{HTTP:VIA} ^.+pinappleproxy [NC]
RewriteRule .* - [F]

Attention! I can not provide any guarantees if it will work in all cases. If you feel like trying it out with your responsibility, go ahead.

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