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Cellular Network Security

Secure Systems Administration Spring 2011. Cellular Network Security. Ryan Stepanek. A brief history of cellular networks. Cellular networks have been deployed for the last three decades 1G networks had maxspeeds of about 9.6 kbs [1]

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Cellular Network Security

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  1. Secure Systems Administration Spring 2011 Cellular Network Security Ryan Stepanek

  2. A brief history of cellular networks • Cellular networks have been deployed for the last three decades • 1G networks had maxspeeds of about 9.6 kbs [1] • As network technology evolved, two standards emerged: CDMA and GSM • Modern cellular networks operate in the third and fourth generation, reaching theoretical speeds up to 100 Mbit/s

  3. Challenges of Cellular Networks • Open Access Wireless – No physical connection necessary! • Bandwidth Limitations – Everyone has to share the network. • System Complexity – The larger the implementation of the system the more difficult it is to maintain security. • Confidentiality – Private data needs to be encrypted. • Integrity – Must minimize data loss; more services being sent through the network. • Authentication With Other Networks – Companies need to play nice with each other.

  4. Security Issue for Cellular Networks • Operating systems on mobile devices – Android, Windows, iPhone • Web services – Potential for abuse through the addition of new services; DOS. • Location Detection – Keep the location of the user private! • Spyware; malware – Phones and network may be vulnerable.

  5. Phone OS by Market Share

  6. Phone OS Market Share – US, UK, China

  7. I-Security • Mobile OS – left open to viruses and malware • Users can jailbreak and run their own code • History of being slow to patch • SMS virus – over two months to patch! • Spreading the virus required only the victims phone number • Spread through memory corruption in iPhone[6] • Potentially detrimental to host network • Dangerously popular – In December 2009 AT&T was forced to halt iPhone sales in New York[5] • Can you hear me now? Network load became too great for existing infrastructure

  8. Blackberries • Very good encryption • Causes conflicts with governments on the grounds of national security • i.e. India 2009[7] • Relies on security through obscurity • Vulnerable through third party apps • i.e. the Webkit browser was used at this year’s Pwn2Own hacking expo.[8] • Blackberry Enterprise Server(BES) • Commonly used in business and government, compromising the server could allow access to phone information • Fairly secure if configured correctly(EAL 4+)[10]

  9. Android • Open source • Incredibly threatening to network profit/security • i.e. free WiFi tethering • Rooting • Allows greater control over the phone • Creates a natural conflict between the service provider and customer • Also increases vulnerability to viruses i.e. custom ROMs will not receive updates from the service provider • Companies now actively trying to hinder rooting i.e. Motorola[8]

  10. GSM vs CDMA • GSM • More than 3.8 billion people worldwide • Far more common outside of North America • More than 89 percent of market share[4] • More than more than 212 countries and territories[3] • Interferes with some electronics • CDMA • Transmits data signal modulated with pseudorandom code • Generally allows for larger transmission cells • Allows users to share frequencies

  11. 3G – Network Components • Radio Access Network • Towers • Radio Network Controllers • Core Network • Packet Switched Network • Circuit Switched Network • SGSN – Handles Access Control and Route Management • GGSN – Gateway to the Internet

  12. 3G – Implementation

  13. Attacks on Cellular Neworks • DOS/DDOS – Probably the most common. • iPhones • Services and bandwidth usage seems to be increasing faster than network infrastrucure • More achievable now through infecting phones • Jamming • Highly localized, similar in effect to DOS • Eavesdropping • Man in the Middle attacks • Session hijacking

  14. 3G - Defensive Measures • Network Access Security • Utilizes secret keys and secret key ciphers to maintain confidentiality • Uses a temporary International Mobile User Identity to protect the user’s identity. • Challenge Response System • Used when Authenticating • Occurs when user first connects to network, when the network receives a service request, when a location update is sent, on attach/detatch request, etc..[1]

  15. 3G-Integrity and Confidentiality • Signaling communications between mobile station and network • F9 algorithm used to calculate 32-bit MAC-I for data integrity then compared to a calculated XMAC-I • F8 used to keep data confidential, utilizes a cipher key that comes from the mobile device; output is then XORed with the original data stream • Both F8 and F9 rely on KASUMI cipher • Based on feistel structure to create 64bit data blocks and a 128 bit key

  16. F8 – Confidentiality Algorithm

  17. 3G-Internet Security • Wireless Application Protocol • Protocol that handles wireless devices connecting to the web • Independent of underlying OS • WAP2 – puts devices into direct communication with servers • Uses layers similar to standard networks • IPv6 and IPv4 • 3G allows for circuit switched and packet switched network nodes • 4G is packet switched nodes only; completely IPv6 compatible

  18. Cellular Network Security – Factors to Consider • Liability • Quantity and nature of data • Potential harm from data • Lawsuits • Profits • Bandwidth is not free • Capability of devices vs. popularity of devices • Risk for every network expansion

  19. Sources • [1] “Security in Wireless Cellular Networks” Gardezi, Ali. http://docs.google.com/viewer?a=v&q=cache:mFeuQOB24gwJ:www1.cse.wustl.edu/~jain/cse574-06/ftp/cellular_security.pdf+cellular+network+security&hl=en&gl=us&pid=bl&srcid=ADGEESgk1O3TVCFitfU0KCDfZp2FIogPvw0bjkw767GFdWlAOyWm866YcuCt8IEn2uag617WAW0S32eIhFbaoMgQiJh_WJi5QYE2RIwkizPeTRzmsFcBNMtESgBQNA9NmF5VgqtrQBe0&sig=AHIEtbR683Y3fhGxdHQa47sZCueMwq3jsA • [2] “Exploiting Vulnerabilities and Security Mechanisms in Internet Based SMS Capable Cellular Networks” Azim, Akramul. http://docs.google.com/viewer?a=v&q=cache:AmTvXrmYVNoJ:citeseerx.ist.psu.edu/viewdoc/download%3Fdoi%3D10.1.1.121.2158%26rep%3Drep1%26type%3Dpdf+cellular+network+security&hl=en&gl=us&pid=bl&srcid=ADGEESiJC2Zr-k8fOWOH70HSEDwahX_x1pJXZOS2AndHNcBqh0Qm3xcBlkqiVgOW0spQM0aqzoMxYkuThzhKiHCKxOa8nc8slQ_qDM1a5OQ_zO0qnBL3Y_9zylwEMLPYr8ORC5mXftkM&sig=AHIEtbQjQIcq5LnEbumpqWogCCN3u0uXVA

  20. Sources - Countinued • [3] “CDMA vs. GSM – Which One is the BestYou?” http://www.cellutips.com/gsm-vs-cdma-which-one-is-the-best-for-you/ • [4] “GSM: Global System for Mobile Communications” http://www.3gamericas.org/index.cfm?fuseaction=page&sectionid=242 • [5] “AT&T apparently resumes online iPhone sales in New York City” http://articles.cnn.com/2009-12-28/tech/iphone.sales.nyc_1_iphone-sales-online-sales-at-t-service?_s=PM:TECH • [6] “First iPhone Virus Found Using SMS Testing” http://ironmill.wordpress.com/2009/07/30/iphone-virus/ • [7] “BlackBerry encryption 'too secure': National security vs. consumer privacy” http://www.zdnet.com/blog/igeneration/blackberry-encryption-too-secure-national-security-vs-consumer-privacy/5732 • [8] “BlackBerry security breached at Pwn2Own 2011” http://crackberry.com/blackberry-security-breached-pwn2own-2011 • [9] “Are the Days of Rooting Android Phones Coming to an End?” http://www.droid-life.com/2011/04/04/are-the-days-of-rooting-android-phones-coming-to-an-end/ • [10] “Approvals and Certifications” http://us.blackberry.com/ataglance/security/certifications.jsp

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