Security threats in wireless cellular networks
Cellular Communication has become an integral part of our everyday life, not only for day-to-day communications but also for accessing the Internet, conducting monetary and business transactions. Limitations of cellular networks, their Network security issues and the threats, Risks, Vulnerabilities and the different types of attacks they are subject to will be discussed.
Wireless cellular networks provide mobile devices access to telephone networks. Cellular networks are composed of single geographical regions covered by a base station called a cell. The base stations then connect the cell to a mobile telephone switching office (MTSO). An MTSO serves a given number of Base Stations in the same geographical area. The MTSO connects to other MTSOs through a Public Switched Telephone Network (PSTN). Each base station has a channel assigned. Base station far apart may have similar channels assigned in a way that limits interference within the channels. Several access methods regulate channel allocation BSs and MSs, such as, Code Division Multiple Allocation (CDMA). The popularity of cellular networks was a result of the possibility of reusing radio frequency. In this setting, multiple users are able to access the network at the same time (Zhang & Stojmenovic, 2005).
Importance of the study
Mobile devices are now more capable of processing data than their predecessors a decade ago. Networks on the other hand are increasing their bandwidth offerings and providing more always-on services. These features provide an increased issue of network security especially through denial of service (Chouchane, 2007).
This research is a result of literature review findings on published material relevant to the topic of security threats in cellular networks. Keywords used in the research were cellular network security, threats on cellular networks and vulnerabilities and type of attacks. The literature review relied on internet search results from Google Scholar and Emerald.
Limitations of Wireless Cellular Networks
A number of issues limit the optimal performance of wireless cellular networks. The limitations make wireless networks less reliable than wired networks. The first limitation is that Wireless cellular networks provide an open access medium. The network operates on a wireless channel and therefore does not have a form of physical barricade. Attackers need no equipment to access the network. Secondly, the networks are able to scale up to a given maximum bandwidth. Wireless networks share the same wireless frequency spectrum and therefore are limited on bandwidth amount they can hold. They are governed by the policy of equitable sharing (Gardezi, 2006).
Wirelesses cellular networks are supposed to support mobility. The requirement makes such systems complex and forms one of their limitations. The complexity makes the administration of network security difficult and introduces new loophole that can be exploited by attackers. In order to increase the efficacy of the wireless systems more complexity is added to the system further opening up loopholes. Wireless networks are not connected in a grid structure like wired networks. As a result, each node in the network requires its own power supply. A full-scale deployment of a wireless network therefore consumes more power than a wired network equivalent. In addition to the need for extra power, the functionality of each network node is dependent on its own power supply capacity (Gardezi, 2006).
Wireless networks need processors on every device used to send or receive signals. The speed of the network is therefore proportional to the processing power of the devices that make up the network. Even though the processor power of these devices is increasing, it is yet to reach optimal levels required to carry out exhaustive processing tasks. By relying on radio frequencies, wireless networks are prone to interferences from other wireless networks and systems. The signals transfer within the network also suffers in relation to the density of the network and the number of users in the network. When compared to a wired network, a wireless network is more limited in its reliability because of the errors arising out of the aforementioned influences (Gardezi, 2006).
Cellular Network Security
Network limitations of cellular networks present a number of security issues. As cellular networked are scaled up in their capacity, they become more complex and deplorers need to be extra careful while fixing security loopholes so as not to create others. Networks function well when all users can be authenticated. Cellular networks face a burden of authenticating a large number of users. Batch authentication of users is not yet possible and each user is authenticated individually every time they access the network. In addition, of authenticating every point of instance, wireless cellular networks have to be interconnected to other cellular networks to facilitate communication across borders. The requirement brings up additional authentication tasks that require a very robust and powerful system. Failure to ensure that the system is robust and well guarded allows attacker to have anonymous access. In the event of a network compromise, network administrators are unable to verify the source of attack. Authentication problems also become national security issues when they face a national wireless network. Such a network carries a considerable number of important information such as financial transactions and national security sensitive information.
Cellular networks offer a variety of services. Network subscribers expect that their messages get to their intended recipients without any non-agreed alteration. When there are errors in the network because of interference or non-authorized access, the integrity of the information passing through the network is questioned. Cellular networks must be secure to ensure that conversations are confidential. Eavesdropping abilities should only be conferred to authorized agents in accordance with the law. Cellular devices are now common tools of conversation; as a result, cellular networks handle a lot of sensitive information that should not be allowed to fall in the hands of unintended persons. Such persons might use the information to conduct criminal offences such as blackmailing the conversing parties (Vacca, 2009).
Cellular networks are accessed by cellular devices. The devices are supposed to be restricted on the amount of data they can submit or extract from the system. In addition to authentication, devices have to be restricted to the levels they can access within the system. Such restriction may be realized through used of different technologies or cryptography software. It is important that even with proper expertise, devices failing to meet a certain technological requirement are unable to access certain limits in a system. Proper access control ensures that the cellular network system is secure (Bragg, Rodhes-Ousley & Strassberg, 2004).
Individual cellular devices are the Achilles’ feet in the network. Vulnerability of one device may compromise the whole network. Cellular phones and other mobile devices such as netbooks and pads that access cellular networks have powerful operating systems. The processing power of such devices now matches that of desktop systems. Previously, such devices only handled end user processing task. With the increased processing power, these devices are able to handle stand-alone processing tasks that cannot be regulated by the network system. The devices use Java Based systems or run their own operating systems. In the event that these systems are compromised, for example being attacked by computer Viruses and Trojans, then they are able to send malicious data into the network system or anonymously obtain sensitive data from the network. Such vulnerabilities when exploited by attackers may be disastrous to cellular networks companies and can destroy a whole network system (Xu, Wood, Trappe & Zhang, 2004).
In addition to the vulnerabilities presented by powerful devices, cellular networks use and offer Web Services to their subscribers. Web Service as a component provides functions that subscriber’s access via the web. Use of the web in accessing these services opens up the network to security threats associated with the standard HTTP protocol. These threats include denial of service attacks and viruses. Cellular networks are now advancing to use their system available resources more efficiently. The network companies are also facing completion pressure to become more innovative in their product offerings. To avoid business extinction, companies are moving their cellular networks to become Internet Protocol (IP) based. IP based systems allocate addresses to each access point in the network. A user’s location therefore becomes searchable since the user is associated with the access point they use to access the system. Such a possibility of locating a cellular device compromises user location privacy (Maxim & Pollino, 2002).
Other than becoming threats indirectly, malware and viruses also offer direct security threats. The wireless networks system is structured in a similar way as other computer system. Increased processing capacity also increases the artificial intelligence level of the system. As the system become more intelligent, they are relied upon to make automatic decisions based on the given parameters. Corrupt system software results to errors across the network. Network wide errors, resulting from malfunctioning, caused by viruses or malware cause unimaginable problems. For example, they can arise to a large-scale denial of service attack; secondly, they can affect the billing system of the cellular network resulting to losses or loss of subscribers because of overbilling.
Web services allow subscribers to download content from the web and such downloads are sometimes infected with spyware and adware. These compromised downloads bring up a security issue since they enhance the other security issues aforementioned. Other than acting as vulnerability points, download services raise copyright issues on digital files. Download and upload services offered by cellular networks allow subscribers to upload and download digital files in any format such as images, music, games and books. Users might download or upload unauthorized copies therefore committing the unlawful act of piracy.
There is need to ensure that only device owners use the devices to access the network. Devices are uniquely identified and in the case of phone, each subscriber is assigned a unique number. When other persons other than the device owner use the device to access the network, then the device owner is charged for a service not personally used. In addition to unwanted charges, unauthorized device use may bring about criminal liabilities when the unauthorized user engages in unlawful acts such as spamming and stalking. Therefore, cellular networks need to be able to disable devices remotely when owners loose them. Other than unauthorized access to the network, unauthorized users of devices get access to personal information like emails, phone numbers and other documents. The remote disabling should be able to make the device deny access to such personal information (Bragg, Rodhes-Ousley & Strassberg, 2004).
Types of Attacks
The denial of service attack (DOS) arises when the network receives excessive data that it cannot handle. The overload causes the network to deny other users access to the service. Users therefore despite having paid for the service and being in a location where the service is available, cannot use it. Such a denial of service exposes the cellular network company to legal sanctions when users sue the company for failing to honor its business end of the subscriber agreements. Denial of service attacks are caused by malware in the system that hogs network capacity. Hogging arises when the malware sends data requests repeatedly at a speed that is faster than the network processor speed of processing the requests. A user operating a single host can also initiate denial of service attack. This case of an attack is more potent than that initiated by a malware or corrupt program. The user initiated attack responds to the changes made by the system in handling incoming request. An attacker can alter the type of request sent to the network when feedback shows that the network system is allocating more resources and is getting faster at handling the attacks.
In order to gain more potency, attackers deploy a distributed denial of service attack. Such an attack uses more than one host and may involve one or more attackers. Attackers may be working as a group or individually, however their cumulative attack power overwhelms the network much faster than a single denial of service attack. A single attacker using a number of hosts may rely on a malware program to compromise the remote access security features such as firewalls present in each host. After successful penetration into host computers, the attacker then remotely initiates attacks using the collective processing power of the captured computers (Lee, Banerjee & Bhattacharjee, 2004).
Attackers can also jam channels in a network. In this case, the jammed network becomes unavailable to other users of the network. Network jamming does not have to an initiate of a host device connected to the network. Attackers may use devices not identifiable by the network system to create unnecessary traffic or block successful delivery of traffic to base stations. A popular form of attack is using an unauthorized access. Attackers gain unauthorized control of devices by developing malware programs and disguising them as genuine. Once they gain access, the attackers may use the devices as host to denial of service attacks as explained above. In addition, attackers can use these victim devices or their own devices to bypass security protocols in the network system. Bypassing is possible when the network authentication system poorly patched. Reasons for poor patching of a network authentication system have featured under the limitations of cellular networks heading above. When attackers gain unauthorized access to the network, they can stop network services, gain access to sensitive information and initiate services within the network to satisfy their own needs. The only way to stop an unauthorized access attack is by making the authentication to be system penetration proof (Bragg, Rodhes-Ousley & Strassberg, 2004).
Eavesdropping is a type of attack where the intruder intercepts sensitive messages. The sensitive message may be in the form of short message services, confidential calls or sensitive digital files. The eavesdropper has to have a device that is capable of intercepting traffic through the network’s wireless link. In addition to having a compatible device, the network has to be unencrypted. In the case where the network is encrypted, the eavesdropper relies on devices with powerful decrypting ability to intercept messages being transmitted within the wireless links. The limitation of wireless networks having no physical barrier further compounds the problem of eavesdropping.
Message forgery as a network attack happens when the communication channel is unsecure. Attackers intercept messages and alter them before resending them to the intended recipient. The recipient is oblivious of the corruption of the messages. In the same manner, the attacker may intercept replies from the recipient and corrupt them before returning them to their initial course. Effects of this kind of attack include the falsification of a sender’s impression of the recipient. For example, a sender may receive a response indication that the recipient has denied a suggestion in a matter discussed when in actual reality the recipient agreed to the matter.
Other than forging messages, attackers can carry out message replay attacks. Replay attacks are possible even when the network has secure communication channels. When the security measure employed by the network system is encryption, attackers can intercept messages and access them later after they manage to decrypt. Other than personal access, the attacker might resend the message to the recipient and fool the recipient that the message is genuine (Pagani, 2005).
A man in the middle attack exploits the wireless no barrier limitation of cellular networks. In this type of attack, message interception occurs between a cell phone and an access station such as a base station. Using appropriate devices, the attacker carry out other forms of attack after interception such as eavesdropping and message manipulation. The final type of attack is session hijacking. In this kind of attack, an already established connection between a network service and a device is hijacked. The hijacker then takes over the session as the legitimate service provider. The user unknowingly then offers personal data to the hijacker and receives data from the hijacker. Software or services accessed from the hijacker may thereafter compromise the user’s device and remotely gain control to carry out other forms of attacks (Bragg, Rodhes-Ousley & Strassberg, 2004).
Individual Device Attack Prevention Measures
Individual devices are the most vulnerable in the architecture of cellular networks. Using firewall software on devises helps to prevent unauthorized intrusions. Most operating systems come with firewall default features and users are encouraged to have the firewall on. Secondly, users should only access trusted networks to limit their exposure to attackers. When using an unsecured network like a public Wi-Fi hotspot, users are encouraged to access internet services that do not require transfer of sensitive data like passwords within the network. Thirdly, when not using wireless connection on mobile devices such as netbooks, users should turn off their wireless adapters. Turning off wireless adapters is the safest way to cushion one against any type of attack. Users should also consider encrypting their signals so that they reduce their vulnerability to eavesdropping and message manipulation attacks. Encryption allows only the intended recipient who has appropriate decryption software, to receive the message. Apart from using technological enhancement to protect one’s device. Personal integrity should always come first as a protective measure. Users should interact and engage web services with caution. It is best to have a personal policy of trusting no one. Preventive steps initiated by the user make the task of breaking into the cellular network, using the user’s mobile device, a nightmare for intruders. Finally, users should always alert the relevant authorities like the police and their network provider when they lose their mobile devices. Early alert allows the company to disengage the service provision to the service identification number or code assigned to the device. This prevents any other person to use the device within the cellular network. To safeguard personal information stored in the devices, users should use access restrictions tools such as passwords, hidden files and hard drive encryption (Nichols & Lekkas, 2002).
Network Attack Monitoring Tools
The honeyd is a background running software (daemon) that cheats a network system by creating nonexistent hosts. Such hosts are virtually recognized in the network but cannot be physically place. A honeyd can imitate any operating system functions and is used by network security administrators to fix vulnerabilities in their networks. The honeyd lures hackers and other attackers into the network by providing easy access point entries. Network administrators then monitor how the attackers break into the dummy system and use their findings to fix entry loopholes in the real network. NTOP is a network analysis tool that monitors network traffic. The tool allows network administrators and engineers to measure traffic and network optimization. Additional capabilities of the NTOP tool include detection of network security violations and allowing the generations of alarms to alert the network operator of any breaches. Finally, the NTOP allows the operator to keep database records of traffic information (Patil et. al. 2002).
Emerging Threats of Wireless Cellular Networks
Cellular network companies have deployed 4G or are eyeing its deployment. 4G allows roaming of devices within multiple wireless and mobile networks. 4G promises to give users unmatched experiences in accessing different services as well as having an increased coverage. 4G users require only one device to get access to the multiple services and therefore enjoy a simplified billing process. As 4G becomes a reality, networks have to supports increased demand for Quality of Service (QoS). Networks have to fulfill QoS in ensuring that varying bit rates, different channel characteristics are all supported in the heterogeneous network. In addition, to providing service challenges, 4G networks come with increased vulnerabilities to Denial of Service attacks. The meshing of different wireless networks and provision of all access to a single device makes the reality of a distributed denial of service attack more vivid (Varshney, & Jain, 2001).
The advancement of cellular network from 2G to 4G has increased their functionality and their vulnerabilities to malicious attacks. Increased functionality of cellular networks has led to its popularity as a medium of providing services like web other than voice that is synonymous with the first deployments of these networks.
The main methods used to secure wireless cellular networks are authentication and encryption. As cellular networks become more advanced, owner companies are investing more into the realization of more secure installations. Research is ongoing into better ways of managing wireless cellular networks. Among the limitation of cellular networks, their wireless nature makes them barrier less. Therefore, intruders have a much easier penetration task than with wired works. Finally, the most potent and frequent type of attack on wireless cellular networks is distributed denial of service attacks.
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