How can you use NGINX logs to detect and mitigate security threats?

1 What are NGINX logs?

NGINX logs are files that record the details of every request and response that the web server processes. NGINX logs can be divided into two types: access logs and error logs. Access logs contain information such as the client IP address, the requested URI, the response status code, the response size, and the user agent. Error logs contain information such as the error level, the error message, and the source file and line number. NGINX logs can be configured to include custom variables and formats, depending on your needs and preferences.

2 How to access NGINX logs?

NGINX logs are usually stored in the /var/log/nginx directory on Linux systems, unless you specify a different location in your NGINX configuration file. You can use various commands and tools to access and analyze NGINX logs, such as tail, grep, awk, sed, cat, less, and more. For example, you can use the tail command to view the latest entries in the access log: tail -f /var/log/nginx/access.log You can also use the grep command to filter the log entries by a specific keyword or pattern, such as a status code or an IP address: grep "404" /var/log/nginx/access.log

3 How to detect security threats from NGINX logs?

NGINX logs can reveal signs of security threats by displaying unusual or malicious requests and responses. For instance, you may observe a high number of requests from a single IP address or range of IP addresses, which could indicate a brute force attack or denial-of-service attack. It's also possible to detect requests with long or complex URI parameters, suspicious or malformed user agents, scripts or tags in the URI or referer header, as well as responses with status codes such as 400, 401, 403, 404, 500, or 503. All of these could be signs of an error or failure in your web server configuration or application logic.

4 How to mitigate security threats from NGINX logs?

NGINX logs can be used to mitigate security threats by providing information that can be used to block or limit malicious requests or responses. For instance, the deny directive can be utilized to block requests from certain IP addresses or ranges, while the limit_req or limit_conn modules can be employed to restrict the number of requests or connections per IP address or per server. Additionally, the rewrite or return directives can redirect or reject requests that match certain patterns or conditions, such as invalid URI parameters or user agents. Furthermore, the add_header directive can add security-related headers to your responses, such as Content-Security-Policy, X-Frame-Options, X-XSS-Protection, and X-Content-Type-Options, to prevent cross-site scripting, clickjacking, and content sniffing attacks. Lastly, the ngx_http_secure_link_module can generate and verify secure links for resources in order to prevent unauthorized access or tampering.

5 How to use tools to enhance NGINX log analysis and security?

Enhancing NGINX logs with tools can help collect, parse, visualize, and monitor log data as well as alert of any security issues. For example, using Fluentd, Logstash, or Filebeat to send NGINX logs to a central location or log management system like Elasticsearch, Splunk, or Datadog. Additionally, Kibana, Grafana, or Loggly can be used to visualize and explore the log data while creating dashboards and reports that show key metrics and trends. Finally, Fail2ban, ModSecurity, or Naxsi can monitor the logs and apply rules and actions to block or ban malicious requests or responses based on predefined or custom criteria such as failed login attempts, SQL injections, or web shell attacks.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?