HowTo: Nginx Block User Agent

How do I block a http user agent or a software agent using Nginx web server under Linux or Unix like operating systems?

You can block any http user agents with GET / POST requests that scrape your content or try to exploit software vulnerability. Use the following syntax. Edit /usr/local/nginx/conf/nginx.conf file, enter:
# vi /usr/local/nginx/conf/nginx.conf
In this example, block http user agent called wget:

## Block http user agent - wget ##
if ($http_user_agent ~* (Wget) ) {
   return 403;
}
 
## Block Software download user agents ##
     if ($http_user_agent ~* LWP::Simple|BBBike|wget) {
            return 403;
     }

Save and close the file. Reload nginx web server, enter:
# service nginx reload
OR
# /usr/local/nginx/sbin/nginx -s reload

How do I block multiple http user agents?

Use the following syntax:

if ($http_user_agent ~ (agent1|agent2|Foo|Wget|Catall Spider|AcoiRobot) ) {
    return 403;
}

Case insensitive blocking: ~* vs ~

Please note the ~* makes it case insensitive as opposed to just a ~:

### case sensitive http user agent blocking  ###
if ($http_user_agent ~ (Catall Spider|AcoiRobot) ) {
    return 403;
}
### case insensitive http user agent blocking  ###
if ($http_user_agent ~* (foo|bar) ) {
    return 403;
}

###用!~*除foo和bar以外全都返回403###
if ($http_user_agent !~* (foo|bar) ) {
    return 403;
}

If you want to know all of the existing user agent strings, check the user agent string website; it has all of the user agent strings that you will ever need.