Ban User Agents module does not work

For example, I enter entry: AhrefsBot. iTSec plugin automatically writed entry to the .htaccess file:

RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} ^AhrefsBot [NC]
RewriteRule ^.* – [F]

But module does not work. May be there are not enough quotation marks?
May be need “^AhrefsBot”? The plugin does not add quotation marks.