Pablo Guides

# Course #184 – Firewalk$ Basics and Advanced Techniques

## Section 1 – Introduction to Firewalk$

Firewalk$ is a powerful tool used in the realm of network security and penetration testing. It operates by sending specially crafted packets to identify open ports and services on a target network, even those that are behind firewalls. In this section, we will cover the installation and configuration of Firewalk$ on Kali Linux, detailed usage instructions, real-world use cases, and technical explanations to help you understand the underlying mechanics of the tool.

### 1.1 Installation and Configuration on Kali Linux

Kali Linux is a Debian-based distribution specifically designed for digital forensics and penetration testing, making it an ideal platform for tools like Firewalk$.

#### Prerequisites

Before installing Firewalk$, ensure you have the following prerequisites installed:

– **Kali Linux** (latest version recommended)
– **Root privileges** for installation

##### Step 1: Update your system

Open your terminal and update your package lists to ensure you have the latest packages.

"`bash
sudo apt update && sudo apt upgrade -y
"`

##### Step 2: Install Firewalk$

Firewalk$ is included in the Kali Linux repositories, making it easy to install. Run the following command:

"`bash
sudo apt install firewalk
"`

##### Step 3: Verify Installation

To confirm that Firewalk$ has been installed successfully, check the version by running:

"`bash
firewalk -V
"`

You should see the version number of Firewalk$ displayed in the terminal.

#### Configuration

Firewalk$ does not require extensive configuration out of the box, but you might need to configure the network settings based on your testing environment. Ensure that your network interface is set up correctly. You can check your network interfaces using:

"`bash
ifconfig
"`

Make note of the interface you plan to use for testing (e.g., `eth0` or `wlan0`).

### 1.2 Step-by-Step Usage and Real-World Use Cases

Now that Firewalk$ is installed, let’s dive into its usage with various commands and options available.

#### Basic Usage Syntax

The basic syntax of Firewalk$ is as follows:

"`bash
firewalk [options] -p -i
"`

**Where:**
– `-p` specifies the target IP.
– `-i` specifies the network interface.

#### Step-by-Step Usage

##### Step 1: Discovering Active Hosts

Before using Firewalk$, you might want to discover active hosts in your network. You can use tools like `nmap` to perform this task:

"`bash
nmap -sn
"`

##### Step 2: Running Firewalk$

To execute Firewalk$, use the following command structure:

"`bash
firewalk -p -i
"`

**Example:**

"`bash
firewalk -p 192.168.1.1 -i eth0
"`

This command sends packets to the specified target IP address over the specified interface.

##### Step 3: Analyze Output

Firewalk$ will send TCP SYN packets to the target and analyze the replies. Here’s an example of output you might see:

"`
Firewalk 5.0 – [Basic information]
Target IP: 192.168.1.1
Port Scan: [Results]
"`

#### Real-World Use Cases

1. **Firewall Testing**: Use Firewalk$ to assess the effectiveness of a firewall by trying to identify its open ports.
2. **Network Reconnaissance**: Helps in gathering information about services running behind firewalls, which aids in further penetration testing.
3. **Vulnerability Assessment**: When combined with other tools, Firewalk$ can help validate the presence of specific security vulnerabilities.

### 1.3 Detailed Technical Explanations and External Reference Links

#### Understanding the Mechanism

Firewalk$ uses a technique known as TTL (Time to Live) expiration to determine the state of a firewall. When a packet traverses a router or firewall, the TTL is decremented. If the TTL reaches zero, the packet is discarded, and an ICMP "TTL expired" message is sent back to the sender.

##### Packet Creation

Firewalk$ creates packets with varying TTL values. By observing whether the responses are ICMP messages or TCP resets, the tool deduces the status of a port.

#### Important Options

– `-h`: Display help information.
– `-p`: Specify a target IP.
– `-i`: Define the interface to use.
– `-t`: Set a custom TTL value.

#### External References

– [Firewalk GitHub Repository](https://github.com/somewhere/firewalk)
– [Official Firewalk Documentation](https://www.kali.org/tools/firewalk/)
– [Nmap Official Documentation](https://nmap.org/docs.html)

### 1.4 Code Examples

Here are some code snippets to help you with common Firewalk$ usage scenarios.

#### Example: Basic Firewall Test

"`bash
firewalk -p 172.16.0.1 -i eth0
"`

#### Example: Advanced Options

Execute with a custom TTL:

"`bash
firewalk -p 172.16.0.1 -i eth0 -t 10
"`

#### Example: Output Redirection

To save results to a text file for later analysis:

"`bash
firewalk -p 172.16.0.1 -i eth0 > results.txt
"`

### Conclusion

Firewalk$ is a potent tool for penetration testers looking to understand the configuration and security posture of firewalls. By following this introductory section, you’ve learned how to install, configure, and use Firewalk$ effectively in real-world scenarios. As you progress in your penetration testing journey, consider combining Firewalk$ with other tools for a comprehensive security assessment.

—

Made by pablo rotem / פבלו רותם