Chapter 7 - Wireless Network Security

Class: CSCE-465-63860

Wireless Security

Some of the key factors contributing to the higher security risk of wireless networks compared to wired networks include

• Channel
  • Wireless networking typically involves broadcast communications, which is far more susceptible to eavesdropping and jamming than wired networks
  • Wireless networks are also more vulnerable to active attacks that exploit vulnerabilities in communications protocols
• Mobility
  • Wireless devices are far more portable and mobile than wired devices
  • Mobility results in a number of risks (theft, malware, risky network connections)
• Resources
  • Small wireless devices, such as smartphones, tablets, IoT devices, can have sophisticated operating systems but are limited in ability to counter threats, including denial of service and malware
• Accessibility
  • Some wireless devices, such as IoT devices and robots, may be left unattended in remote and/or hostile locations
  • Leaving devices unattended greatly increases their vulnerability to physical attacks

Wireless Network Threats

Accidental association

• Company wireless LANs in close proximity may create overlapping transmission ranges
• A user intending to connect to one LAN may unintentionally lock on to a wireless access point from a neighboring network

Malicious association

• In this situation, a wireless device is configured to appear to be a legitimate access point, enabling the operator to steal passwords from legitimate users and then penetrate a wired network through a legitimate wireless access point

Ad hoc networks

• These are peer-to-peer networks between wireless computers with no access point between them
• Such networks can pose a security threat due to a lack of a central point of control (authentication issue)
• E.g. WiFi Direct

Nontraditional networks

• Personal network, Bluetooth devices, wireless barcode readers, keyboards, IoT devices all pose a security risk in terms of both eavesdropping and spoofing. Some are pretty safe, some not

Identity theft (MAC spoofing)

• This occurs when an attacker is able to eavesdrop on network traffic and identify the MAC address of a computer with network privilege

Man-in-the-middle attacks

• This attack involves persuading a user and an access point to believe that they are talking to each other when in fact the communication is going through an intermediate attacking device
• Wireless networks are particularly vulnerable to such attack

Denial of service (DoS)

• This attack occurs when an attacker continually bombards a wireless access point or some other accessible wireless port with various protocol messages designed to consume system resources
• The wireless environment lends itself to this type of attack because it is so easy for the attacker to direct multiple wireless messages at the target

Network injection

• This attack targets wireless access points that are exposed to nonfiltered network traffic, such as routing protocol messages or network management messages

Securing Wireless Transmissions

• The principal threats to wireless transmission are eavesdropping, altering or inserting messages, and DoS attacks
• To deal with eavesdropping, two types of countermeasures are common:
  • Signal-hiding techniques
    • Turn off SSID broadcasting by wireless access points
    • Assign cryptic names to SSIDs (and SSID broadcast off)
    • Reduce signal strength to the lowest level that still provides coverage
    • Locate wireless access points in the interior of the building, away from windows and exterior walls
  • Encryption
    • Is effective against eavesdropping to the extent that the encryption keys are secured – and algorithms are strong

Securing Wireless Access Points

• The main threat involving wireless access points is unauthorized access to the network
• The principal approach for preventing such access is the IEEE 802.1x standard for port-based network access control
  • The standard provides authentication mechanism (EAP) for devices wishing to attach to a LAN or wireless network
  • The use of 802.1x can prevent rogue access points and other unauthorized devices from becoming insecure backdoors or serve as man-in-the-middl

Securing Wireless Networks in General

• Use encryption / strong algorithms
• Use antivirus, antispyware software and a firewall
• Turn off SSID broadcasting
• Change SSID on your router from the default
• Change your router’s pre-set password for administration to a strong password
• Use access control, but not depending on shared password (may also restrict on MAC address)

Mobile Device Security

• Mobile devices have become an essential element for organizations as part of the overall network infrastructure
• Prior to the widespread use of smartphones, network security was based upon clearly defined perimeters that separated trusted internal networks from the untrusted Internet
• An organization’s networks must therefore accommodate:
  • Growing use of “new” devices
  • Cloud-based applications
  • De-perimeterization
  • External business requirements

Security Threats

Major security concerns for mobile devices:

• Lack of physical security control
  • The security policy for mobile devices must be based on the assumption that any mobile device may be stolen or at least accessed by a malicious party
• Use of untrusted mobile devices
  • The organization must assume that not all devices are trustworthy
• Use of untrusted networks
  • The security policy must be based on the assumption that the networks between the mobile device and the organization are not trustworthy
• Use of untrusted content
  • Mobile devices may access and use content that other computing devices do not encounter
• Use of applications created by unknown parties
  • It is easy to find and install third-party applications on mobile devices and this poses the risk of installing malicious software
• Interaction with other systems
  • Unless an organization has control of all the devices involved in synchronization, there is considerable risk of the organization’s data being stored in an unsecured (or not GDPR compliant) location, plus the risk of the introduction of malware
• Use of location services
  • An attacker can use location information to determine where the device and user are located, which may be of use to the attacker

IEEE 802.11 Wireless LAN Overview

• IEEE 802 is a committee that has developed standards for a wide range of local area networks (LANs)
• In 1990 the IEEE 802 Committee formed a new working group, IEEE 802.11, with a charter to develop a protocol and transmission specifications for wireless LANs (WLANs)
• Since that time, the demand for WLANs at different frequencies and data rates has exploded

Wi-Fi Alliance

• Wireless Ethernet Compatibility Alliance (WECA)
  • An industry consortium formed in 1999
  • Subsequently renamed the Wi-Fi (Wireless Fidelity) Alliance
  • Created a test suite to certify interoperability for 802.11 products
• Wi-Fi
  • The term used for certified (in beginning) 802.11b products
  • Extended to 802.11g, 802.11a, 802.11n, …., products
  • https://en.wikipedia.org/wiki/IEEE_802.11
• Wi-Fi security
  • Wi-Fi Alliance has developed certification procedures for IEEE 802.11 security standards
  • Referred to as Wi-Fi Protected Access (WPA, WPA2, WPA3)

IEEE 802.11 Terminology

IEEE 802.11 Services

Association-Related Services

• Transition types based on mobility:

  • No transition
    • A station of this type is either stationary or moves only within the direct communication range of the communicating stations of a single BSS
  • BSS transition
    • This is defined as a station movement from one BSS to another BSS within the same ESS
    • In this case, delivery of data to the station requires that the addressing capability be able to recognize the new location of the station (same IP subnet)
  • ESS transition
    • This is defined as a station movement from a BSS in one ESS to a BSS within another ESS
    • Maintenance of upper-layer connections (e.g., TCP, UDP) supported by 802.11 cannot be guaranteed
    • Disruption of service is likely to occur (another IP subne

• To deliver a message within a DS, the distribution service needs to know the identity (MAC address) of the AP to which the message should be delivered in order for that message to reach the destination station

  • Solution: Self-learning feature of switch at link layer

• Three services relate to a station maintaining an association with the AP within its current BSS:

  • Association
    • Establishes an initial association between a station and an AP
  • Reassociation
    • Enables an established association to be transferred from one AP to another, allowing a mobile station to move from one BSS to another
  • Disassociation
    • A notification from either a station or an AP that an existing association is terminated
    • Q: What if a laptop is just switched off?

IEEE 802.11i Wireless LAN Security

• There is an increased need for robust security services and mechanisms for wireless LANs
  • Wired Equivalent Privacy (WEP)
    • The privacy portion of the 802.11 standard
    • COntained major weakness
  • Wi-Fi Protected Access (WPA)
    • A set of security mechanisms that eliminates most 802.11 security issues
    • Based on a not final version of 802.11i standard
  • Robust Security Network (RSN/WPA2)
    • Final form of the 802.11i standard
    • Complex
  • Robust Security Network 2018 Update (RSN/WPA3
    • Specification of improved WPA2
    • Not yet a part of 802.11i standard

Protected Data Transfer Phase

• IEEE 802.11i defines two schemes for protecting data transmitted in 802.11 MPDUs
  • Temporal Key Integrity Protocol (TKIP)
    • Designed to require only software changes to old devices that are implemented with WEP
  • Counter Mode-CBC MAC Protocol (CCMP)
    • Intended for newer IEEE 802.11 devices that are equipped with the hardware to support this scheme (AES encryption hw)
• Provides two services:
  • Message integrity
  • Data confidentiality

IEEE 802.1X Access Control Approach

• Port-Based Network Access Control
• The authentication protocol that is used, the Extensible Authentication Protocol (EAP), is defined in the IEEE 802.1X standard
• 802.1X uses:
  • Controlled ports
    • Allows the exchange of PDUs between a supplicant and other systems on the LAN only if the current state of the supplicant authorizes such an exchange
  • Uncontrolled ports
    • Allows the exchange of PDUs between the supplicant and the AS, regardless of the authentication state of the supplicant

IEEE 802.11i Keys for Data Confidentiality and Integrity Protocols

Pairwise Keys

• Used for communication between a pair of devices, typically between a STA and an AP
  • These keys form a hierarchy beginning with a master key from which other keys are derived dynamically and used for a limited period of time
• Pre-shared key (PSK)
  • A secret key shared by the AP and a STA and installed in some fashion outside the scope of IEEE 802.11i
• Master session key (MSK)
  • Also known as AAAK, and is generated using the IEEE 802.1X protocol during the authentication phase
• Pairwise master key (PMK)
  • Derived from the master key
  • If a PSK is used, then the PSK is used as the PMK; if a MSK is used, then the PMK is derived from the MSK by truncation
• Pairwise transient key (PTK)
  • Consists of three keys to be used for communication between a STA and AP after they have been mutually authenticated
  • Using the STA and AP addresses in the generation of the PTK provides protection against session hijacking and impersonation; using nonces provides additional random keying mate
  • Forward secrecy?

Group Keys

• Group keys are used for multicast communication in which one STA sends MPDUs to multiple STAs
  • Group master key (GMK)
    • Key-generating key used with other inputs to derive the GTK
  • Group temporal key (GTK)
    • Generated by the AP and transmitted to its associated STAs
    • IEEE 802.11i requires that its value is computationally indistinguishable from random
    • Distributed securely using the pairwise keys that are already established
    • Is changed every time a device leaves the network, but how to know…..

IEEE 802.11i Pseudorandom Function (PRF)

• Used at a number of places in the IEEE 802.11i scheme (to generate nonces, to expand pairwise keys, to generate the GTK)
  • Best security practice dictates that different pseudorandom number streams be used for these different purposes
• Built on the use of HMAC-SHA-1 to generate a pseudorandom bit stream
• RFC 1750 (Randomness Recommendations for Security)

Summary

• Wireless network security
  • Network threats
  • Security measures
• Mobile device security
  • Security threats
  • Security strategy
• IEEE 802.11 wireless LAN overview
  • Wi-Fi Alliance
  • IEEE 802 protocol architecture
  • IEEE 802.11 network components and architectural model
  • IEEE 802.11 services
• IEEE 802.11i wireless LAN security
  • IEEE 802.11i services
  • IEEE 802.11i phases of operation
  • Discovery phase
  • Authentication phase
  • Key management phase
  • Protected data transfer phase
  • The IEEE 802.11i pseudorandom function