How to Perform Security Testing Using Nuclei: An Extensive Guide

Nuclei is a powerful and highly customizable vulnerability scanning tool, widely used for security testing across various protocols, such as HTTP, DNS, and TCP. Developed by ProjectDiscovery, it allows cybersecurity professionals to automate the detection of vulnerabilities by leveraging YAML-based templates. This open-source tool provides flexibility in creating custom workflows and integrating with other tools, making it ideal for continuous security testing.

1. Installation and Setup

To begin using Nuclei, you must first install the Go programming language. Then, you can install Nuclei via the following command:

GO111MODULE=on go get -v github.com/projectdiscovery/nuclei/v2/cmd/nuclei

Once installed, update the vulnerability templates with:

nuclei -update-templates

This will ensure you have the latest templates for vulnerability scanning.

2. Basic Usage

The simplest way to run Nuclei is to scan targets using a pre-defined list of templates. For example:

nuclei -l targets.txt -t cves/

This command scans the URLs listed in targets.txt for known CVEs (Common Vulnerabilities and Exposures). The results can be filtered by severity using the -severity flag to focus on critical or high vulnerabilities:

nuclei -t cves/ -severity critical,high -l targets.txt

3. Creating and Using Custom Templates

One of the most powerful features of Nuclei is its ability to use custom YAML-based templates. These templates define specific tests for vulnerabilities, and creating one is straightforward. Here’s an example template:

id: custom-vulnerability

info:

name: Custom Vulnerability

author: your-name

severity: high

description: Detects a custom vulnerability

requests:

- method: GET

path:

- "{{BaseURL}}/vulnerable-endpoint"

matchers:

- type: word

words: ["vulnerable"]

Once your template is ready, you can scan a target like this:

nuclei -u https://example.com -t /path/to/custom-template.yaml

4. Optimizing Performance

Nuclei allows you to control the rate of requests and the number of concurrent threads to balance speed and server load:

nuclei -l targets.txt -rl 50 -c 10

This will limit the tool to 50 requests per second and use 10 concurrent threads.

5. Integrating Nuclei with CI/CD Pipelines

Nuclei can be integrated into CI/CD pipelines to ensure continuous vulnerability scanning. For example, in GitHub Actions, you can create a workflow file that installs Nuclei and runs a scan on each push or pull request:

name: Nuclei Scan

on: [push, pull_request]

jobs:

nuclei:

runs-on: ubuntu-latest

steps:

- name: Checkout code

uses: actions/checkout@v2

- name: Install Nuclei

run: |

sudo apt update

sudo apt install nuclei

- name: Run Nuclei Scan

run: |

nuclei -u https://your-app.com -t /path/to/template.yaml

6. Reporting

Nuclei supports various output formats for reporting, such as JSON and HTML:

nuclei -u https://example.com -t /path/to/template.yaml -json -o report.json

This will save the results in report.json for further analysis or integration with other tools.

7. Advanced Scanning and Workflows

Nuclei also supports running multiple templates simultaneously using workflows:

nuclei -w workflows/wordpress-workflow.yaml -l targets.txt

This command runs a set of templates in the wordpress-workflow.yaml file, allowing for more complex and tailored scans.

Conclusion

Nuclei is an essential tool for automating vulnerability scanning, and its open-source nature makes it an evolving platform, supported by a large community of contributors. Whether integrated into CI/CD pipelines or used manually, Nuclei provides flexibility and efficiency in identifying potential security issues across web applications and network infrastructure.