How to use Nginx to prevent apache flag injection attacks

In the field of network security, Apache flag injection attack is a relatively common attack method. Attackers use certain vulnerabilities or specific HTTP request parameters to forge request headers, thereby tricking the server into performing unexpected operations or executing Malicious code. To prevent this attack, we can use Nginx as a reverse proxy server to handle requests. The following describes how to use Nginx to prevent Apache flag injection attacks.

1. Set Nginx reverse proxy

When Nginx processes a request, it can forward the request to the back-end server and filter out certain request headers to avoid forged requests. , thus improving the security of the system. When configuring Nginx reverse proxy, you need to use Apache as the backend server and filter out specific data in the request header.

The configuration is as follows:

server {
  listen 80;
  server_name example.com;
  location / {
    proxy_pass http://apache_server;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_set_header X-Nginx-Proxy true;
    proxy_set_header Connection "";
    if ( $http_user_agent ~* (libwww-perl|wget) ) {
    return 403;
    }
    if ( $http_host ~* "^[0-9]+.[0-9]+.[0-9]+.[0-9]+$" ) {
    return 403;
    }
    if ( $http_referer ~* "(babes|forsale|girl|jewelry|
      love|nudit|organic|poker|porn|sex|teen)" ) {
    return 403;
    }
  }
}

In this configuration, we use the proxy_set_header directive, which can dynamically add the data in the request header to each reverse proxy request. For example, we can add X-Real-IP to the Apache server. This directive can also filter out some unsafe requests, such as requests that indicate automated attacks such as libwww-perl or wget in the user agent, or requests in which the referer field in the request contains sensitive words such as porn.

2. Configuring the firewall

In order to further ensure system security, we also need to configure the firewall on the server. The rules are as follows:

iptables -I INPUT -p tcp --dport 80 -m string --algo bm --string "apache" -j DROP

This configuration can be done in iptables Add a filtering rule to filter out all requests containing the string "apache". This rule can effectively filter out some malicious requests, thus improving the stability and security of the system.

3. Install mod_security

In order to further improve the security of the server, we can also install the mod_security module, which can perform in-depth security checks on requests on the Apache server. For example, checking whether the request contains a series of advanced attacks such as SQL injection attacks, and designing flexible rules can effectively prevent malicious attacks and abuse and ensure the security and reliability of the server.

4. Set up SSL

If you need to handle sensitive information or a website similar to e-commerce, we also need to use an SSL certificate to ensure the encryption and secure transmission of data. By using an SSL certificate, you can prevent data from being stolen or tampered with during transmission, ensuring user privacy and security.

Summary

By using Nginx as a reverse proxy server, you can filter out some security risks and malicious requests and improve the security and reliability of the server. The security of the server is further enhanced by measures such as firewalling and installing mod_security. In applications such as handling sensitive information and e-commerce, we recommend using SSL certificates to ensure the secure transmission of data and comprehensively improve the security and stability of the server.

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