How to Hack WiFi (Wireless) Network
Wireless
networks are accessible to anyone within the router’s transmission
radius. This makes them vulnerable to
attacks. Hotspots are available in public places such as airports, restaurants,
parks, etc.
In this
tutorial, we will introduce you to common techniques used to exploit
weaknesses in wireless network security implementations. We will also look
at some of the countermeasures you can put in place to protect against such
attacks.
What
is a wireless network?
A wireless
network is a network that uses radio waves to link computers and other devices
together. The implementation is done at the Layer 1 (physical layer) of the OSI
model.
How
to access a wireless network?
You will need a
wireless network enabled device such as a laptop, tablet, smartphones, etc. You
will also need to be within the transmission radius of a wireless network
access point. Most devices (if the wireless network option is turned on) will
provide you with a list of available networks. If the network is not password
protected, then you just have to click on connect. If it is password protected,
then you will need the password to gain access.
Wireless
Network Authentication
Since the
network is easily accessible to everyone with a wireless network enabled
device, most networks are password protected. Let’s look at some of the most
commonly used authentication techniques.
WEP
WEP is the
acronym for Wired Equivalent Privacy. It was developed for IEEE 802.11 WLAN
standards. Its goal was to provide the privacy equivalent to that provided by
wired networks. WEP works by encrypting the data been transmitted over the
network to keep it safe from eavesdropping.
WEP
Authentication
Open System
Authentication (OSA) – this methods grants access to station authentication
requested based on the configured access policy.
Shared Key
Authentication (SKA) – This method sends to an encrypted challenge to the
station requesting access. The station encrypts the challenge with its key then
responds. If the encrypted challenge matches the AP value, then access is
granted.
WEP
Weakness
WEP has
significant design flaws and vulnerabilities.
- The integrity of the packets is
checked using Cyclic Redundancy Check (CRC32). CRC32 integrity check can be compromised by
capturing at least two packets. The bits in the encrypted stream and the
checksum can be modified by the attacker so that the packet is accepted by
the authentication system. This leads to unauthorized access to the
network.
- WEP uses the RC4 encryption
algorithm to create stream ciphers. The
stream cipher input is made up of an initial value (IV) and a secret key.
The length of the initial value (IV) is 24 bits long while the
secret key can either be 40 bits or 104 bits long. The total length of
both the initial value and secret can either be 64 bits or 128 bits long.The
lower possible value of the secret key makes it easy to crack it.
- Weak Initial values
combinations do not encrypt sufficiently.
This makes them vulnerable to attacks.
- WEP is based on passwords; this
makes it vulnerable to dictionary attacks.
- Keys management is poorly
implemented. Changing keys especially on
large networks is challenging. WEP does not provide a centralized key
management system.
- The Initial values can be
reused
Because of
these security flaws, WEP has been deprecated in favor of WPA
WPA
WPA
is the acronym for Wi-Fi Protected Access.
It is a security protocol developed by the Wi-Fi Alliance in response to the
weaknesses found in WEP. It is used to encrypt data on 802.11 WLANs. It uses
higher Initial Values 48 bits instead of the 24 bits that WEP uses. It
uses temporal keys to encrypt packets.
WPA
Weaknesses
- The collision avoidance
implementation can be broken
- It is vulnerable to denial of
service attacks
- Pre-shares keys use
passphrases. Weak passphrases are vulnerable to dictionary attacks.
How
to Crack Wireless Networks
WEP
cracking
Cracking is the
process of exploiting security weaknesses in wireless networks and gaining
unauthorized access. WEP cracking refers to exploits on networks that use WEP
to implement security controls. There are basically two types of cracks namely;
- Passive cracking– this type of cracking has no effect on the network
traffic until the WEP security has been cracked. It is difficult to
detect.
- Active cracking– this type of attack has an increased load effect on
the network traffic. It is easy to detect compared to passive cracking. It
is more effective compared to passive cracking.
WEP
Cracking Tools
WPA
Cracking
WPA uses a 256
pre-shared key or passphrase for authentications. Short passphrases are
vulnerable to dictionary attacks and other attacks that can be used to crack
passwords. The following tools can be used to crack WPA keys.
General
Attack types
- Sniffing– this involves intercepting packets as they are
transmitted over a network. The captured data can then be decoded using
tools such as Cain & Abel.
- Man in the Middle (MITM) Attack– this involves eavesdropping on a network and
capturing sensitive information.
- Denial of Service Attack– the main intent of this attack is to deny legitimate
users network resources. FataJack can be used to perform this
type of attack.
Cracking
Wireless network WEP/WPA keys
It is possible
to crack the WEP/WPA keys used to gain access to a wireless network. Doing so
requires software and hardware resources, and patience. The success of such
attacks can also depend on how active and inactive the users of the target
network are.
We will provide
you with basic information that can help you get started. Backtrack is a
Linux-based security operating system. It is developed on top of Ubuntu.
Backtrack comes with a number of security tools. Backtrack can be used to
gather information, assess vulnerabilities and perform exploits among other
things.
Some of the
popular tools that backtrack has includes;
- Metasploit
- Wireshark
- Aircrack-ng
- NMap
- Ophcrack
Cracking
wireless network keys requires patience and resources mentioned above. At
a minimum, you will need the following tools
A wireless
network adapter with the capability to inject packets (Hardware)
- Kali Operating System. You can download it from here https://www.kali.org/downloads/
- Be within the target network’s
radius. If the users of the target
network are actively using and connecting to it, then your chances of
cracking it will be significantly improved.
- Sufficient knowledge of
Linux based operating systems and working knowledge of Aircrack and
its various scripts.
- Patience, cracking the keys may take a bit of sometime
depending on a number of factors some of which may be beyond your control.
Factors beyond your control include users of the target network using it
actively as you sniff data packets.
How
to Secure wireless networks
In minimizing
wireless network attacks; an organization can adopt the following policies
- Changing default passwords that come with the hardware
- Enabling the authentication
mechanism
- Access to the network can be
restricted by allowing only
registered MAC addresses.
- Use of strong WEP and WPA-PSK
keys, a combination of symbols,
number and characters reduce the chance of the keys been cracking using
dictionary and brute force attacks.
- Firewall Software can also help reduce unauthorized
access.
Hacking
Activity: Crack Wireless Password
In this
practical scenario, we are going touse Cain and Abel to decode the stored
wireless network passwords in Windows. We will also provide useful
information that can be used to crack the WEP and WPA keys of wireless networks.
Decoding
Wireless network passwords stored in Windows
- Download Cain & Abel from
the link provided above.
- Open Cain and Abel
- Ensure that the Decoders tab is
selected then click on Wireless Passwords from the navigation menu on the
left-hand side
- Click on the button with a plus
sign
- Assuming you have connected to
a secured wireless network before, you will get results similar to the
ones shown below
- The decoder will show you the
encryption type, SSID and the password that was used.
Summary
- Wireless network transmission
waves can be seen by outsiders, this possesses many security risks.
- WEP is the acronym for Wired Equivalent
Privacy. It has security flaws which make it easier to break compared to
other security implementations.
- WPA is the acronym for Wi-Fi
Protected Access. It has security compared to WEP
- Intrusion Detection Systems can
help detect unauthorized access
- A good security policy can help
protect a network.