How to Ensure the Security of Mobile Networks

February 24, 2024

Mobile networking refers to the infrastructure and technologies that enable mobile devices, such as smartphones and tablets, to connect and communicate with each other and with the internet. It involves the transmission of voice, data, and multimedia content over wireless networks.

 

Introduction to Mobile Networking:

 

Mobile networking encompasses wireless wide-area networking, which includes traditional cellular data communication technologies found in mobile phones, along with emerging low-power wide-area network (LPWAN) technologies like LoRa, LoRaWAN, and SigFox. These LPWAN technologies offer long-range wireless data communication, prioritizing battery power conservation over high data rates. Additionally, newer cellular technologies such as Narrowband IoT (NB-IoT), EC-GSM-IoT, and LTE-M (or LTE-MTC) are also utilized for mobile networking in the context of the Internet of Things (IoT).

 

Generations of Cellular Protocols:

 

Each generation of cellular technologies is categorized by a "G" (e.g., 2G, 3G, 4G, 5G), which represents the generation's specific data transmission rates and distinct over-the-air encoding methods. As each new generation is introduced, it typically becomes incompatible with the previous ones due to these technological advancements.

 

1.    First-generation (1G):    

It Refers to analog cellular technologies.

2.     Second-generation (2G): Includes digital cellular technologies like CDMA, GSM, and TDMA. It introduced features such as SMS messaging and voicemail.

 

3.     Third-generation (3G): Comprises digital cellular technologies such as EVDO, HSPA, and UMTS. It offers faster data rates compared to 2G, enabling mobile web browsing, image sharing, and GPS location sharing.

 

 

4.     Fourth-generation (4G): Encompasses digital cellular technologies like WiMAX and LTE. It provides even faster data rates than 3G, reaching up to hundreds of megabits per second.

 

5.     Fifth-generation (5G): Involves digital cellular technologies with data rates exceeding 1 gigabit per second. It offers lower latency (faster turnaround) and greater bandwidth, enabling support for a higher number of connected devices.

 

Please note that the information provided above is a general overview of the different generations of cellular technologies and may not encompass all the specific technical details or variations within each generation.

 

Cellular Protocols:

A summary of significant cellular communication protocols is given below:

 

Ø Global System for Mobile Communications (GSM):

 

The Global System for Mobile Communications (GSM), established by the European Telecommunications Standards Institute (ETSI) in 1991, is a standard that defines the protocols utilized in second-generation (2G) digital cellular networks for devices like mobile phones and tablets. With the exception of the United States and Russia, GSM has become the widely adopted standard for mobile communication worldwide. One significant aspect of GSM networks is the utilization of SIM cards, which play a crucial role. These cards store the service subscription, network identification, and potentially address book data. They are essential for provisioning IoT devices and phones, as they hold the identity and cryptographic keys necessary for secure communication.

 

Ø General Packet Radio Service (GPRS):

 

A cellular data standard, established in 1993 and developed by ETSI, is built upon the global communication networks of GSM (2G and 3G cellular). It provides a framework for IoT devices and phones to be provisioned using SIM cards, which securely store identity and cryptographic keys. To ensure data security, encryption is applied at the Logical Link Control (LLC) Layer, utilizing the GPRS Encryption Algorithm (GEA).

 

Ø Universal Mobile Telecommunications System (UMTS):

 

UMTS (Universal Mobile Telecommunications System) is a third-generation cellular standard that originated from GSM and was developed by 3GPP (3rd Generation Partnership Project). It was introduced in 1999 as an advancement in mobile communication technology. UMTS incorporates data encryption using the KASUMI algorithm, employing a 128-bit cipher key to ensure secure transmission. This standard supports both encryption and data integrity protection, enhancing the overall security of cellular communications.

 

Ø Code Division Multiple Access (CDMA):

 

CDMA (Code Division Multiple Access) technology was originally formulated in Russia during the 1930s and was subsequently utilized by the Allied Forces in World War II to counteract radio signal jamming. In contrast to GSM, CDMA-based cellular service grants users unrestricted access to the entire range of radio bands, allowing a larger number of users to connect simultaneously. CDMA has commonly been employed in the United States and Russia, alongside GSM. Unlike GSM, CDMA does not rely on SIM cards for user identification. Instead, devices must be specifically designed for compatibility with a particular carrier's network.

 

Ø Long-Term Evolution (LTE):

 

LTE (Long-Term Evolution) is a wireless service that, from a technical standpoint, falls under the category of third-generation technology, despite being marketed as 4G LTE or Advanced 4G. It builds upon the foundations of GSM and UMTS technologies. The 3GPP (3rd Generation Partnership Project) played a key role in developing this standard. Various countries utilize different LTE frequencies and bands, necessitating multi-band phones to fully access LTE across all regions.

 

Ø 5G (Fifth-generation):

 

The primary goal of 5G technology is to bring high-speed broadband capabilities to a global network. It offers data rates that are at least ten times faster than those provided by 4G LTE, along with significantly lower latency, facilitating faster two-way communication between devices. These attributes make 5G particularly well-suited for various types of IoT communications. It's important to note that the radio system used in 5G is incompatible with 4G. However, in the United States, early 5G networks will initially be non-standalone (NSA), meaning they will require the presence of a 4G network to establish the initial cellular connection. In areas where 5G is available, it will be utilized, while 4G will continue to be used in areas without 5G coverage.

 

Cellular Communications in IoT:

Currently, there is a range of cellular technologies in use, with older technologies like CDMA and GSM gradually declining in popularity while newer technologies like 5G are on the rise. The increasing adoption of IoT is a significant driving force behind the demand for 5G. 5G networks offer extremely high data rates and have the capacity to connect millions of devices simultaneously. Although non-cellular forms of networking are more prevalent in IoT deployments, the introduction of 5G may lead to a notable shift towards cellular connectivity for IoT devices. In fact, 5G has the potential to replace Wi-Fi or wired networks in certain scenarios. With 5G, there is the possibility of establishing more direct communication paths between IoT devices and cloud services, reducing the reliance on IoT gateways. This, in turn, reduces the attack surface of IoT gateways. However, this shift introduces new components and security concerns when IoT devices communicate directly with cloud services.

 

Custom APNs:

An Access Point Name (APN) serves as a gateway connecting a cellular network to another computer network, such as a company's TCP/IP network. Mobile devices are configured with an APN that specifies the type of data connection the mobile carrier should establish when the device connects to the cellular network. The APN contains essential information like assigned IP addresses, security methods, and the ultimate destination network for the device. Organizations have the flexibility to define a custom APN, allowing them to control and route IoT traffic through a cellular network while maintaining some level of oversight.

 

By implementing a custom APN, organizations can direct IoT traffic to their private network, enabling the application of specific security controls before the traffic reaches the broader internet. This approach empowers organizations to monitor traffic flows using Intrusion Detection Systems (IDS) equipped with rule sets designed to identify and flag any suspicious or abnormal activity. Additionally, encryption protocols can be applied to ensure the confidentiality of data as it traverses the internet. Detailed traffic logs can be created for later analysis, and various other operations can be performed to enhance security and operational management.

 

The use of a custom APN allows organizations to optimize the transport of IoT data through a cellular network while maintaining control and implementing robust security measures. It provides the flexibility to direct traffic to specific networks, apply encryption, leverage monitoring systems, and perform advanced analysis, facilitating enhanced security and management of IoT communications.

 

Threats to Cellular Communication:

While cellular data connections are generally considered secure, it is important to acknowledge that they are not immune to compromise. Vulnerabilities do exist, even in 4G LTE networks. However, security experts note that exploiting these vulnerabilities would typically require specialized tools and significant effort. As a result, attackers are more likely to target high-value entities where the effort and cost of an attack would be justified.

The security of cellular networks remains an ongoing focus, with continuous efforts to enhance their protections. Newer technologies like 5G and improved iterations of 4G are expected to provide even stronger security measures. Identified vulnerabilities in GSM networks, for instance, have led to security enhancements over time. Possible vulnerabilities might include:

  • Insertion of malicious base stations
  • Weak keys (due to a low bit count)
  • Cleartext transmission of keys across the network

Mobile Client Security:

 

Cellular data connections can offer more secure network connections for IoT client applications on mobile devices compared to Wi-Fi. Users often connect to unsecured Wi-Fi hotspots without distinguishing between encrypted and unencrypted networks, which exposes their application communications and web browsing activity to potential interception. In contrast, cellular networks encrypt data within the network itself, adding an extra layer of security on top of application-level encryption. While cellular networks are not entirely immune to vulnerabilities, they generally provide a safer option compared to unencrypted public Wi-Fi hotspots for most users.

 

Threats to Low-Power Mobile Devices:

 

Low-power mobile IoT devices, including those that utilize technologies like LoRa, LoRaWAN, and SigFox, are particularly prone to malicious interference and vulnerabilities compared to other network-connected mobile devices.

The following are various vulnerabilities that low-power wide-area networks may be subject to:

 

 Authentication:  

Authentication poses a distinct challenge for low-power mobile devices due to their limited computational capabilities. Public-key cryptography, which is commonly used for authentication, can be computationally intensive and resource-consuming for these devices. Insufficient authentication mechanisms may leave devices vulnerable to data reading or spoofing by malicious actors. Furthermore, even if low-power devices can handle the cryptographic functions, the processing time required can introduce latency issues, particularly when real-time or near real-time communication is essential.

 

Updates:

The low data rates offered by certain mobile network technologies can pose difficulties in maintaining devices' security through regular patching and updates. These devices, often found in remote locations, are typically cost-effective and intended for long-term deployment, which increases the risk of devices being lost, forgotten, or neglected over time. Despite this, these devices remain connected to the network, presenting an additional attack surface that can be exploited by malicious actors.

 

Complexity of security protocols:

LPWAN networks often face challenges with security protocols due to the characteristics of low-power mobile devices. Security protocols typically involve large data packets that can become fragmented during transmission, requiring frequent reassembly. However, low-power devices may lack sufficient energy, processing power, or memory to handle the complex task of assembling and disassembling these fragmented packets. This limitation can hinder the effective implementation of security measures in LPWAN networks.

 

Key management:

The use of symmetric encryption in IoT introduces the need to securely store keys in multiple locations. However, IoT devices' vulnerabilities can make key compromise more likely, emphasizing the importance of implementing robust security measures to protect these keys.

 

Beacons:

Certain mobile communication protocols utilize beacon broadcasts to identify devices within a particular range on the network. However, if these messages lack authentication, encryption, or signing mechanisms, they become susceptible to spoofing. Unsecured beacons can serve as a source of information for attackers and provide an avenue for injecting malicious data into the system. Implementing robust authentication, encryption, and signing measures is crucial to mitigate the risks associated with beacon vulnerabilities and ensure the integrity and security of the network.

 

How to Secure Mobile Networks - To secure your mobile networks for use in IoT:

 

v  Examine the "joining" or "pairing" process for each mobile network your system uses and implement controls to ensure that rogue devices cannot join the network. Please avoid using or implementing such networks that sacrifice security to make joining the web easy.

 

v  Educate end-users to utilize cellular data connections instead of public Wi-Fi when using mobile application clients.

 

v  When supporting scenarios where mobile IoT clients connect via public Wi-Fi, ensure the use of a VPN or strong application-level encryption to safeguard data.

 

 

v  Implement secure key storage practices by storing keys in a secure manner and limiting access to specific devices that require them.

 

v  Generate a unique key pair for each mobile IoT device communicating with the server. This approach ensures that if the keys on one device are compromised, the security of other devices will not be compromised.

 

 

By following these guidelines, you can enhance the security posture of mobile IoT deployments, mitigating risks associated with public Wi-Fi usage and protecting sensitive data transmitted by IoT devices.

 

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