Wi-Fi Security Audit: Vulnerability Testing in Kali Linux

Today's wireless networks are complex ecosystems where data security is the number one priority for administrators and router owners. Kali Linux — is a specialized distribution created by information security professionals for legal penetration testing. Unlike standard operating systems, it contains a pre-installed set of utilities for traffic analysis, port scanning, and password strength testing.

It is important to understand that using these tools against other people's networks without the owner's written permission is a violation of the law. Ethical hacking implies work exclusively within one's own perimeter or under a contract. The purpose of this material is to demonstrate how administrators identify weaknesses in a configuration. wireless networks, in order to then eliminate them and protect users' data from real attackers.

The audit process begins with a thorough understanding of Wi-Fi architecture and encryption principles. Without a theoretical foundation, practical application of tools can lead to network equipment blocking or data loss. The most vulnerable link in the security chain is often not the encryption protocol, but a weak password, selected by brute force. Therefore, the main focus in Kali Linux is shifted to checking the strength of authentication.

Preparing equipment and environment for audit

The first step in the testing process is proper hardware preparation. Standard built-in Wi-Fi modules in laptops often don't support necessary operating modes, such as monitoring and packet injection. For full functionality, an external USB adapter based on chipsets is required. Atheros AR9271 or Ralink RT3070These devices are capable of switching to a mode that allows them to "listen" to the entire broadcast, not just traffic addressed to a specific device.

After connecting the adapter, you need to launch the terminal and check its status. The command iwconfig will display a list of available interfaces. If the adapter is detected correctly, its name will usually look like this: wlan0 or wlan1The next critical step is switching the interface to monitor mode. This state allows the card to capture all packets within range, bypassing the need to connect to an access point.

A utility is often used to translate the interface. airmon-ngThe process requires stopping interfering system processes, such as network managers, that may be taking control of the adapter. After the command is successfully executed airmon-ng start wlan0 a virtual monitoring interface is created, usually with a suffix mon, For example, wlan0monAll further data collection operations will take place through it.

Scanning the airwaves and searching for target networks

During the reconnaissance phase, the specialist's task is to detect all available wireless networks in the field of view. Tool airodump-ng is the de facto standard for this operation. It displays a list of SSIDs (network names), access point MAC addresses (BSSIDs), channels used, and encryption types. Information on the number of connected clients and signal strength is updated on the screen in real time.

The analyst points out several key parameters. First, the encryption type: networks using outdated WEP, are vulnerable almost instantly, whereas WPA2-PSK requires more sophisticated attacks. Secondly, the presence of active clients. Some types of attacks require at least one connected user on the network whose packets can be intercepted for subsequent analysis.

The command to start the scan looks like this:

airodump-ng wlan0mon

After finding a network of interest, scanning can be limited to a specific channel and BSSID for more detailed data collection. This allows you to create a special capture file, which stores all passing packets. This file will serve as the basis for further cryptanalytic work. It's important not to miss the moment a new client joins the network, as their authorization process (handshake) contains encrypted password hashes.

WPA/WPA2 Handshake Analysis

The key to modern Wi-Fi network security is the four-way handshake. This is where the client device and access point exchange encrypted data to confirm knowledge of the password, without transmitting the password in plaintext. An auditor's job is to intercept this packet exchange. If there are already active users on the network, the handshake can simply be waited for and saved.

However, it is often necessary to speed up the process or trigger it. For this, the deauthentication method is used. Using the utility aireplay-ng Special control frames are sent on behalf of the access point to the client, requesting that the connection be terminated. Upon receiving such a request, the client automatically attempts to reconnect, generating a new handshake, which is immediately captured by the collection tool.

The command to force deauthentication looks like this:

aireplay-ng --deauth 10 -a [BSSID] -c [Client MAC] wlan0mon

Here is the parameter --deauth 10 Specifies the number of break packets sent. A successful handshake capture is displayed in the upper right corner of the window. airodump-ng with the corresponding message. The resulting file with the handshake hash is ready to be passed to the password checking module. Without this file, further brute-force attempts are impossible.

Password Cracking Methods: Dictionaries and Brute-Force

Once the handshake hash is successfully captured, the cryptanalysis phase begins. Since encryption algorithms AESThe keys used in WPA2 are mathematically secure; directly cracking the key is impossible in a reasonable amount of time. The only way is to guess the password used to generate it. For this purpose, a combination of tools is most often used in Kali Linux. hashcat or john (John the Ripper).

There are two main approaches. The first is a dictionary attack. The program checks the hash against a list of common passwords. The second is brute-force, which tries every possible character combination. Brute-force is only effective for short passwords, as the time it takes to crack them increases exponentially with length. For complex passwords of 12+ characters, brute-force can take years.

Example of running a dictionary check in hashcat:

hashcat -m 2500 capture.hccapx wordlist.txt

The effectiveness of this stage directly depends on the quality of the dictionary. Professional auditors use combined databases containing millions of leaked passwords, proper names, dates, and typical combinations. If a user's password is found in such a dictionary, it can be found in seconds. However, if the password is a random string of characters, the chances of success are minimal without the use of powerful GPU clusters.

WPS Attacks and Configuration Vulnerabilities

In addition to password brute-force attacks, there is an attack vector targeting the Wi-Fi Protected Setup (WPS) function, which is designed to simplify device connections. The WPS protocol has a fundamental design flaw: the PIN code consists of only eight digits, the last of which serves as a checksum. This reduces the number of possible combinations to 11,000, making it possible to brute-force them in just a few hours, even on a regular laptop.

Tool reaver or its more modern version bully They automate this process. They try to guess the PIN code, after which the router automatically gives up the password for the main network. However, modern equipment manufacturers have implemented protections: blocking after several unsuccessful attempts or completely disabling the WPS function. Nevertheless, on devices with older software or cheaper models, this method still works effectively.

⚠️ Warning: Using tools like reaver This creates a huge flood of requests to the access point, which can cause it to freeze or reboot. On some routers, this can temporarily block the WPS function for several hours.

Also worth mentioning are Evil Twin attacks. Here, a fake access point is created with the same name (SSID) as the legitimate one, but with a stronger signal. Users can accidentally connect to it, and their password requests will be redirected to a phishing page. This is social engineering, which bypasses technical security measures, requiring users to be vigilant.

Protecting your network from unauthorized access

Understanding attack methods allows you to formulate effective defense strategies. The first and most important step is to avoid using WPS. If you don't need the feature, you should disable it in your router settings. This will close one of the easiest doors for attackers. You should also ensure that the encryption protocol is used. WPA3 or, at least, WPA2-AES. TKIP and WEP protocols should be excluded completely.

The length and complexity of a password are crucial. A password of 20 random characters, including numbers, uppercase and lowercase letters, and special characters, makes a brute-force attack theoretically possible, but practically impossible in the foreseeable future. Regularly updating your router's firmware is also critical, as manufacturers patch security holes discovered by researchers.

Network segmentation provides an additional layer of protection. Guest networks should be isolated from the main local network, where computers with sensitive data and smart home devices are located. This will prevent lateral movement (movement within the network) in the event of a compromise of one of the guest devices.

Legal aspects and ethics

Working with Kali Linux tools requires a clear understanding of legal boundaries. In most countries, creating a hacking tool is not a crime, but using it on someone else's system without the owner's consent falls under criminal law provisions on unauthorized access to computer information. Even attempting to connect to an open network for traffic analysis can be considered a violation unless the network owner has explicitly granted permission.

Professional pentesters always work under a signed contract (Scope of Work), which clearly defines testing boundaries, timeframes, and permitted methods. Violating these boundaries can lead to legal action. Ethical hacking is primarily about responsibility and compliance with the law, and only then about technical skill.

⚠️ Please note: Cybersecurity legislation is constantly changing. Before beginning any work, be sure to familiarize yourself with the current regulations in your region and obtain written confirmation of your right to test your infrastructure.

The knowledge gained should be used to strengthen defenses. Network administrators are required to regularly conduct self-assessments using the methods described to identify weaknesses before malicious actors exploit them. Only a proactive approach ensures true data security in today's digital world.

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