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  2. 2. VoIP VULNERABILITIES The following report outlines characteristics of Voice over Internet Protocol (VoIP). It explains the benefits and history of VoIP. Then it describes current VoIP standards and the security risks and vulnerabilities that surround the technology. In addition, particular attention is drawn to Skype, currently the most popular VoIP application in use today.
  3. 3. TABLE of coNTENTS Table of Contents Table of contents .................................................................................. 3 Introduction ............................................................................................. 4 VoIP Benefits ............................................................................................ 5 VoIP History .............................................................................................. 6 VoIP Standards........................................................................................ 7 H.323............................................................................................................. 8 Session Initiation Protocol (SIP) .................................................... 9 VoIP Vulnerabilities ............................................................................10 Risks & Vulnerabilities Inherited from IP .............................. 11 Risks & Vulnerabilities Associated with VoIP ......................12 Risks & Vulnerabilities Specific to VoIP ..................................14 Skype..........................................................................................................17 Conclusion ..............................................................................................19 References...............................................................................................20 Disclaimer Information....................................................................21 VoIP VULNERABILITIES | MATTHEW HURLEY
  4. 4. INTRodUcTIoN V oIP is defined as the ability to make telephone calls, associated with VoIP, and those specific to VoIP. Firstly, send faxes and carry out video-conferencing over an overview of the benefits of VoIP. IP based networks. This is achieved by utilising current VoIP standards and protocols such as H.323, Session Initiation Protocol (SIP), and Skype to convert analogue signals into digital data that can be transmitted over the Internet. VoIP offers a number of benefits including increased flexibility and reduced overheads to any organisation that is willing to change its voice networks from the traditional circuit switched network to that of the packet switched network utilised by VoIP. Even though the traditional Public Switched Telephone Network (PSTN) has proven to be highly reliable over the past 135 years, VoIP is seen as a more promising alternative. This is because VoIP is more effective when utilizing available bandwidth and also allows for more efficient network deployment models. Taking the above into account, it is not hard to understand that the number of VoIP subscribers has steadily increased to 18.1 million users worldwide as at the end of 2005 . It has also been projected that the number of VoIP subscribers will more than double to 47 million subscribers by the end of 2006 . Like any new IT service, VoIP has a large number of inherent and associated security risks and vulnerabilities that can affect the reliability and availability of an organisations IT infrastructure. It is also one of the major issues slowing the uptake of VoIP. Therefore it is paramount for any organisation looking to incorporate VoIP to have a total understanding of the threats that they will be potentially introducing into their IP networks. This report classifies the risks and vulnerabilities of VoIP into three categories 1those inherited from IP, 2those 1 http://clickz.com/showPage.html?page=3623253 2 http://lw.pennnet.com/Articles/Article_Display.cfm?ARTICLE_ ID=267354p=13 CCIP INFORMATION NOTE - ISSUE 06
  5. 5. VoIP BENEfITS T here are two major benefits to any organisation or business wanting to implement VoIP in their day-to-day operations. The first major benefits is the would facilitate call savings of at least $5,000 dollars a year. However consultants in the industry state that call savings are only a small part of the overall benefits lower costs associated with VoIP when compared to gained by a VoIP system. The major benefits come from that of the traditional PSTN. The main reasons VoIP is the simplified infrastructure and with it the reduced considered more economical include: management and maintenance costs. • Reduced cost of phone calls: The costs of phone The second major benefit of VoIP is increased flexibility calls via VoIP are minuscule when compared to and location independence. These additional benefits equivalent calls made over the traditional PSTN. emphasize the advantages to be gained by any This is because VoIP takes advantage of existing organisation implementing the technology and show WAN connectivity to remote locations over a that VoIP is more than simply just a way to reduce dedicated data network or the Internet, thus expenditure. They include: avoiding any long-distance toll-call charges. • Improved flexibility: VoIP allows for new helpful • Reduced maintenance and capital costs: VoIP is features like ‘click-to-call’ that enable a user to based on software rather than purely hardware, simply click a URL while browsing a web page therefore it is easier to alter and maintain. that will initiate a call over a VoIP network to an Furthermore deploying a VoIP network can be attendant. less expensive when compared with the costs • Improved productivity: A Virtual Private Network of deploying a Private Branch Exchange (PBX). (VPN) combined with VoIP can be used to set • Simplified infrastructure: Because VoIP up a fully functioning office anywhere there utilises the same infrastructure as your data is a broadband connection. Furthermore VoIP network its possible to converge the two, thus treats voice as if it were any other kind of data, so simplifying the operation and management of users can attach documents to voice messages the network. This is also advantageous from a or participate in virtual meetings using shared cost perspective as a single network can carry data and videoconferencing. both voice and data. • Location Independence: This allows an The financial gain provided by VoIP obviously depends individual to have incoming phone calls on the size of the business and how that particular automatically routed to their office or personal business operates. One particular business case, VoIP phone number regardless of location. This provided by Deloitte’s New Zealand, showed the initial is because when using a VoIP network, the user VoIP setup cost for a medium sized business of 350 only needs to be able to register their location employees would be close to $225,000. This figure with the VoIP server to be able to receive calls. includes an incremental capital investment of $125,000 as it would approximately cost $100,000 to replace the existing analogue system. Once installed the system VoIP VULNERABILITIES | MATTHEW HURLEY
  6. 6. VoIP HISToRy T he history of VoIP dates back to 1964 when Paul Baran wrote the first paper on secure packetised voice. However, it was not until thirty-one years later in 1995 that the first internet phone software ‘Vocaltec’ was released. Coincidently it was in May of the same year that the International Telecommunications Union (ITU) initiated work on the H.323 standard. The next major development in VoIP occurred in September of 1999 when work was commenced on the popular SIP by the Internet Engineering Task Force (IETF). SIP was then accepted as a 3rd Generation Partnership Project (3GPP) signalling protocol in November 2000. The following year Microsoft incorporated VoIP into Windows XP Messenger using SIP. This was closely followed by the founding of Vonage, which is a leading provider of broadband telephone services with over 2 million subscribers in 2006. The last major development in VoIP came in August of 2003 with the release of Skype. CCIP INFORMATION NOTE - ISSUE 06
  7. 7. VoIP STANdARdS There are two major non proprietary standards used for VoIP communications by many VoIP software applications. They are H.323 and Session Initiation Protocol (SIP). VoIP VULNERABILITIES | MATTHEW HURLEY
  8. 8. H.2 H .323 is a protocol suite specified by the ITU that lays a foundation for IP based real-time communications including audio, video and data. H.323 was designed to handle call setup and tear-down functions and can use both TCP and UDP as a transport mechanism. Security within the H.323 protocol is achieved by the H.235 protocol, which incorporates four security goals including authentication, integrity, privacy, and non-repudiation. These goals are provided through four mechanisms, namely: configuration, authentication, key exchange, and encryption. Security concerns within H.323 arise as many of the protocols use random ports causing problems securing them through firewalls. This may be mitigated by using direct routed calls, however since the ports required for H.323 are not defined, a filtering firewall would require all possibly-needed ports left open, thus allowing multiple entry points to be exploited by malicious users. CCIP INFORMATION NOTE - ISSUE 06
  9. 9. SESSIoN INITIATIoN PRoTocoL (SIP) S ession Initiation Protocol is a signalling protocol specified by the IETF, used to set up and tear down two-way communications sessions. Security in SIP is SIP’s registrations and communication mechanisms. It is possible to resolve NAT issues when using VoIP but this usually requires innovative solutions. similar to H.323 and aims to achieve confidentiality, message integrity, non-repudiation, authentication and privacy. SIP has a security advantage over H.323 as it uses only one port (traditionally TCP and UDP port 5060). However because SIP operates at the application level, no new security mechanisms were created. Instead SIP’s security is achieved by utilising the security mechanisms provided by HyperText Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), and Internet Protocol Security (IPSec). One of the main security concerns for SIP are that HTTP Digest does not provide adequate integrity, and spoofing of the header would be easily accomplished without employing S/MIME (Secure/Multipurpose Internet Mail Extension). The use of S/MIME for encryption also adds another issue as it uses public key infrastructure, thus making it difficult for users moving between devices as certificates are associated with users. Lastly the text encoding of SIP makes it easier to analyse using standard parsing techniques. The security issues of SIP are highly apparent as there has been over 20,000 uniquely identifiable threats launched against SIP networks in the last two years3. A common security issue for both VoIP standards comes through the use of NAT (Network Address Translation). NAT poses a problem for both H.323 and SIP as it is designed to hide the IP address on the internal network from the public network. Thus causing a disruption firstly, in the ‘setup next’ procedure used by each protocol within the H.323 suite and secondly, inhibiting 3 G. S Sipera, Comprehensive VoIP Security for the Enterprise: Not Just Encryption Authentication, Sipera (March 2006) VoIP VULNERABILITIES | MATTHEW HURLEY
  10. 10. VoIP VULNERABILITIES As VoIP is an IP based technology that utilises the Internet it also inherits all associated IP vulnerabilities. The impact of these Internet-borne attacks is then multiplied by the VoIP architecture as it adds a number of additional weaknesses, which require futher work to secure and maintain. Furthermore, as with adding any new service to an inadequately secured environment, is like piercing holes in an already-leaky boat. The following paragraphs describe the risks and vulnerabilities of VoIP that are firstly, inherited from IP, secondly, associated with VoIP, and lastly, specific to VoIP. 10 CCIP INFORMATION NOTE - ISSUE 06
  11. 11. RISkS VULNERABILITIES INHERITEd fRom IP Poor Architectural design PBX Hosts Gateways Replay Attacks Poor or inadequate architecture Most service interceptions and A replay attack can be mounted can lead to ongoing difficulties in eavesdropping attacks will usually against a VoIP network by the operation and security of a VoIP require the compromise of a PBX retransmitting a legitimate session system. Firewalls are particularly as a means of network access. A so that the recipient device vulnerable areas in a VoIP network compromised host or gateway reprocesses the data. The basis as they require additional ports to can facilitate this by capturing of a replay attack is to capture be opened to facilitate VoIP traffic. voice packets to reveal information a valid packet, which can then Non VoIP-aware firewalls may lack on all calls, call duration, and call be replayed into the network. dynamic interaction with VoIP so parameters. This information will This generally causes the target they simply leave a range of ports permit the mapping of VoIP, and network to respond and provide continually open for call activity. possibly the supporting data more traffic to capture, eventually networks. providing enough information to move to packet spoofing and masquerading, or simply finding an entry point into the target network for eavesdropping. For example a replay attack could be used to gain access to a network by capturing and replaying a valid user ID and password, even though the captured data is encrypted and the attacker was unable to decrypt it. VoIP VULNERABILITIES | MATTHEW HURLEY 11
  12. 12. RISkS VULNERABILITIES ASSocIATEd wITH VoIP Packet Spoofing fuzzing Reconnaissance Attacks masquerading Fuzzing is a legitimate method of Reconnaissance Attacks are a form Packet spoofing uses IP packets testing software systems for bugs of intelligence gathering where with a false source address that may and is accomplished by providing networks are probed to ascertain be used for: an application with semi-valid input their vulnerabilities. Methods used to see what its reaction will be. This to achieve this include call walking • obscuring the origin of the technique can be employed to and port scanning and are the first packet exploit vulnerabilities in a target action undertaken by an attacker • implicating another site or host VoIP system and is achieved by when attempting to penetrate a as the attack originator sending messages so that the network. A successful probe would • masquerading as a trusted host target system will assume the determine the behaviour of the • interception or hijacking of sent content is valid. In reality, the network’s equipment, users, and network traffic message is ‘broken’ or ‘fuzzed’, thus services that might be available • directing responses to another causing various failures to occur to be exploited or disrupted. This host or system when the target system attempts information could then be used to • undertaking man-in-the-middle to parse or process it. Resultant launch a focused attack against the spoofing attacks failures can include application network. A major risk associated with packet delays, information leaks, and spoofing and masquerading is system crashes. identity theft. For example a man- in-the-middle spoofing attack, as shown in Figure 1, can be launched when a person makes a call, which includes sensitive information. As a result of the attack they may speak to the intended recipient however, their call is being monitored by Intended Call Flow malicious users. Re w su ltin Flo gC all Caller A all in gC Caller B Flo lt w su Re Malicious User 12 CCIP INFORMATION NOTE - ISSUE 06
  13. 13. RISkS VULNERABILITIES ASSocIATEd wITH VoIP continued Reliability Availability denial of Service (doS) challenges DoS and Distributed Denial of Service (DDoS) attacks occur when a To achieve constant real time voice malicious user deliberately sends an exceedingly large amount of random communications, VoIP places a high messages to one or more VoIP end-points from either a single location priority on Quality of Service (QoS). (DoS) or from multiple locations (DDoS), as shown in Figure 2. Multiple However the reliability of voice and locations are achieved through the use of zombies (compromised machines data networks is closer to 99.9%, that could be woken upon request and used for malicious purposes). The which compares poorly against DoS attack is successful when the amount of incoming messages exceeds the 99.999% reliability that people the processing capacity of the target system, thereby exhausting system have come to expect from the resources and thus, denying services to the end-users. traditional PSTN. Even though this VoIP systems are especially vulnerable to DoS and DDoS attacks because of doesn’t appear to be a significant the high fundamental requirement that they place on QoS. Therefore less difference it equates to an additional traffic or network disruption is required for a DoS attack to be successful downtime of 8.7 hours each year for when compared to mounting a DoS attack against a data network. A VoIP. This could ultimately lead to further consideration is needed where VoIP and data share the same the loss of human life if emergency network. Here the data network could also be subject to the same DoS services were required during this attack. Examples of VoIP specific DoS attacks include identity spoofing and outage window. cancellation of pending call set up signals, also known as the SIP CANCEL DoS attack. DoS Attack on End Point DDos Attack on Call Server Malicious User VoIP Phone Malicious User VoIP Server Zombies VoIP VULNERABILITIES | MATTHEW HURLEY 1
  14. 14. RISkS VULNERABILITIES SPEcIfIc To VoIP cId Spoofing Phone Impersonation One type of masquerading is based on the manipulation of Caller ID (CID), Phone impersonation occurs which is used to identify the caller before answering, and is known as CID due to the weak authentication spoofing. The CID is based on reported information from different carrier process attributed to VoIP. There switches and is specified by the switch administrator in a VoIP environment. are two major contributors that This allows an attacker to spoof their CID information with a text string or consolidate this fact. Firstly, there is phone number they specify and could be used to give credibility to various a limited human interface available malicious users undertaking social engineering attacks. for VoIP phones, limiting users to the selection of a numeric PIN for In addition to this, the option for CID privacy (i.e. the ability to obscure their password in lieu of a strong your phone number from the CID display) is not possible with VoIP, since password based on the entire the phone number is included in the SIP and H.323 header. This allows any ASCII character set. Secondly, and attacker with a IP packet sniffer, such as tcpdump, to discover the remote this is related to the SIP standard, caller’s phone number, even if their number has been marked as private by the authentication mechanism is their service provider. Further, there are a number of CID spoofing service based on the MD5 algorithm. An providers in the US that, for a small fee, allow users to choose the number attacker who can sniff the entire they are calling from. SIP authentication exchange A recent example of CID spoofing was reported by SpoofCard.com, which is cannot observe the password a company that sells enhanced calling cards that provide the CID spoofing sent in plain text, but can observe ability. Coincidently 50 customer’s accounts were cancelled, including enough information to mount an Paris Hilton’s, due to customers abusing the CID spoofing feature to break offline dictionary attack against into other peoples voice-mail accounts, listen to their messages, and even the password. The combination of change the targeted user’s greetings . 5 these weaknesses allows passwords to be easily obtained by an attacker and then used to impersonate a phone or user. 5 http://voipsa.org/blog/2006/08/28/paris-hilton-hacker-extraordinaire/ 1 CCIP INFORMATION NOTE - ISSUE 06
  15. 15. RISkS VULNERABILITIES SPEcIfIc To VoIP continued Eavesdropping call Hijacking Redirection Eavesdropping is the unauthorised Call hijacking and redirection occurs when a call intended for one user interception of voice packets or Real is redirected to another. To achieve this, an attacker only needs to have Time Protocol (RTP) media streams, knowledge of the user’s authentication credentials in order to impersonate and the decoding of signalling and receive all calls intended for that user. Methods including spoofing of a messages. It is a relatively simple node, man-in-the-middle attacks, and manipulation of call requests using attack to administer and tools such signalling response codes make call hijacking and redirection relatively as network protocol analysers, easy to instigate. Further to this, VoIP features including call forwarding and sniffers and packet capture tools ‘follow-me’ also help facilitate the ability to route calls to specific phone are freely available on the Internet. numbers. Wireshark is an example of a Call hijacking and redirection can also be used for financial gain. For example, tool that can be used to capture call hijacking can be targeted by cyber-criminals who resell the calls. This is VoIP traffic and reconstruct VoIP sometimes used as a money laundering channel from which organisations conversations. would only see an increase in bandwidth usage together with increased A real world example of costs. Similarly, call redirection may also transit another system to collect eavesdropping was publicised in data for later analysis or simply as a revenue gathering mechanism. In this July of 2005 where flaws were found case, the consequences may include the loss of sensitive information and in Cisco’s CallManager VoIP software. service disruption. The flaw could be exploited by Call hijacking was recently discovered in Miami by the US Federal sending specially crafted packets to government. In this particular case Edwin Pena sold discounted Internet the Cisco CallManager that allowed phone services by hacking into other Internet phone providers and an attacker to create a heap overflow piggybacking connections through their networks unbeknown to them. and ultimately enable him to mount In one three-week period a particular Internet phone provider received an eavesdropping attack4. about 500,000 calls that were made to look like they had come from the investment company Rye Brook. Because of this, the victimised Internet phone provider was left having to pay $300,000 in connection fees for routing the phone traffic to other carriers without receiving any revenue for the calls6. 4 http://www.techweb.com/wire/ security/165702369 6 http://voipsa.org/blog/2006/06/07/hacker-cracks-net-phone-providers-for-gain/ VoIP VULNERABILITIES | MATTHEW HURLEY 1
  16. 16. RISkS VULNERABILITIES SPEcIfIc To VoIP continued VoIP Spam these. The above paragraphs also emphasize the fact VoIP SPAM or Spam over Internet Telephony (SPIT) is the that organisations that chose a simplified infrastructure unsolicited and unwanted bulk messages broadcast for both voice and data could experience disruptions to over VoIP to particular end users. Not only could this their data networks if an attack was launched against be extremely annoying (especially when time zones their more vulnerable VoIP network. are taken into consideration), it also has the potential to VoIP is a relatively new technology and research be rather costly where for example, calls are forwarded regarding its security is very young, in fact it is said to mobile phones. Another issue arises with SPIT and to be at the tip of the iceberg. Therefore as additional the fact that high-volume bulk calls routed over IP are research is carried out and new vulnerabilities are very difficult to trace and have the inherent capacity discovered, it would be important for an organisation for fraud, unauthorised resource use, and privacy to consider separating the data and VoIP networks in violations. order to avoid a potential business and or operational Voice mail bombing is a form of SPIT where multiple catastrophe. (this may entail hundreds or even thousands of) voice The following paragraphs will look at Skype, which mail messages flood voice mail boxes. This attack could is the most commonly used VoIP application on the result in service disruption or a denial of service attack. market today. The first real wide spread phishing attack utilising VoIP was launched in June 2006 against customers of the Santa Barbara Bank Trust in Southern California. Targets of the scam were sent an official looking email warning them that their bank account had been locked as a security measure and asked that the recipient call the supplied number to verify the account and user’s identity. When customers called the number they were greeted with an automated voice system requesting that they enter their account number and other personal information7. The above paragraphs explain three different groups of risks and vulnerabilities that can affect the security of a VoIP service or network. They also show that any organisation wanting to utilise this technology needs to be strongly aware of the issues surrounding it and have appropriate security polices in place to mitigate 7 http://www.eweek.com/article2/0,1895,1985966,00.asp 1 CCIP INFORMATION NOTE - ISSUE 06
  17. 17. SkyPE S kype is a proprietary VoIP system developed by However, there are a number of other factors that Skype Technologies and released in August 2003. affect the security of Skype. Firstly, the security of It is the software of choice in the UK, being used by Skype depends on the security of the computer and 48% of VoIP users8. Skype, which recorded a record network on which Skype is running. Secondly, because high of 8 million users online at one time in November Skype uses a proprietary protocol, the only sources 2006, utilises a Peer-to-Peer architecture that relies on a of information regarding any security weaknesses are central authentication sever to authenticate users and statements from the company and publicly disclosed software distributions. In addition to this, both user vulnerabilities. Thirdly, because Skype is mostly a peer- identities and software distributions are digitally signed to-peer system, the overall security can be affected by by an RSA private key. The resulting RSA public key is third parties that are unknown to those in a particular embedded into every Skype executable and thus, phone conversation. The latter is possible as problems provides the basis for voice encryption. have been identified in Skype’s encryption format, which firstly, allows the execution of man-in-the-middle Skype does differ considerably from SIP and H.323 in attacks and secondly, enables the ability for a worm to the way that it connects clients that are sitting behind be hidden in the encryption during transmission10. firewalls. In order to initiate a connection, Skype creates a rendezvous point, also known as a super-node, which These are not the only concerns that affect the security ensures NAT’ed users can communicate with each of Skype. Another issue arises in Skype because it is ‘port- other. A super-node is a computer operating on a public agile’ meaning that if a firewall port is blocked, Skype will IP address that has the ability to proxy connections to seek other open ports to establish a connection. This the Skype clients behind the more restrictive firewalls. feature would also allow an attacker, if a vulnerability Further to this, the total amount of load placed on a was exploited, to use the application to gather further network when a machine becomes a super-node is information about machines on a network. Therefore, unknown and it also has the ability to interfere with Skype could provide a back door into otherwise secure a business’s applications and services. One publicised networks for worms, Trojans, and viruses11. example showed that while a user’s machine was In addition to the above, it was recently shown that acting as a super node, Skype was utilising 100kbps Skype could provide botnet controls that could enable of the company’s bandwidth for both upload and a better way for controlling zombies. What is concerning download dataflows9. about this for an organisation is that any attack (for Super-nodes are not the only concern of the Skype example a DoS attack) resulting from this technology protocol. Security is also a major concern, the key may be virtually impossible to identify the perpetrator. properties being; privacy, authenticity, availability, This is because Skype uses proprietary technology and survivability, resilience, and integrity (of conversation encrypted data traffic that cannot be easily monitored. and system). 10 http://www.skypejournal.com/blog/archives/2005/11/five_reasons_ not_to_block_skype_1.php 8 http://www.eweek.com/article2/0,1895,1985966,00.asp 11 http://computerworld.co.nz/news.nsf/news/ 9 http://www.voipwiki.com/blog/?p=30 1C31DD62E610104ACC2570B40016C985 VoIP VULNERABILITIES | MATTHEW HURLEY 1
  18. 18. SkyPE continued This potential concern could be mitigated by a small group of Chinese engineers who have proved that they have reverse engineered Skype. The redesigned software has a different GUI than the traditional Skype application and can be used to discover the IP address and physical location of the Skype user who you are calling12. Even though Skype has a number of key features, including privacy, authenticity, availability, survivability, resilience, and integrity, in place to ensure its security, the above paragraphs clearly outline that these are far from foolproof. In addition it has also been identified that Skype’s own functionality used to provide its high quality service can also be used for malicious purposes. Also, the concept of hosting a super-node is far from desirable for any organisation that values its bandwidth. Therefore it is important for an organisation to fully understand the security risks of Skype when choosing to use it as their main VoIP application. 12 http://www.voipwiki.com/blog/?p=26 1 CCIP INFORMATION NOTE - ISSUE 06
  19. 19. coNcLUSIoN V oIP offers a number of benefits to any organisation considering implementing it into its day-to- day operations. At the time of writing, organisations have the choice of two VoIP standards and one proprietary protocol (H.323, SIP, and Skype) that can be utilised for lowering the costs of daily operations and increasing flexibility. However, any organisation that has implemented or is looking to implement VoIP needs to be aware of the security issues surrounding the technology. Phone impersonation, reconnaissance attacks, eavesdropping, SPIT, call hijacking and redirection, and identity theft are only a few of the possible risks and vulnerabilities that a malicious person can mount against an organisation’s VoIP service. Therefore, it is important organisations carry out the appropriate security measures to ensure the confidentiality, integrity, and availability of their VoIP, and in some cases, data networks. VoIP VULNERABILITIES | MATTHEW HURLEY 1
  20. 20. REfERENcES 1. S. Garfinkel, VoIP and Skype Security, Skype Security Overview – Rev 1.6 (May 2005) 2. J. Waldron , VoIP Security Essentials, Black Hat Briefings http://www.blackhat.com/presentations/bh-usa- 06/BH-US-06-Waldron.pdf 3. Dr. T. Porter, H.323 Mediated Voice over IP: Protocols, Vulnerabilities Remediation http://www.securityfocus.com/print/ infocus/1782 4. Cyber Security Industry Alliance, Cyber Security for IP Telephony, Findings Recommendations (May 2005) 5. C. Roberts, Voice Over IP Security, Centre for Critical Infrastructure Protection (May 2005) 6. Sipera, Comprehensive VoIP Security for the Enterprise: Not Just Encryption Authentication, Sipera (March 2006) 7. Whichvoip, The History of VoIP http://www.whichvoip.com/voip/articles/voip_ history.htm 8. Dr. R. Kuhn, T. J. Walsh, S. Fries, Security Considerations for Voice Over IP Systems, NIST SP 800-58 9. VoIP – Standards and Protocols http://www2.rad.com/networks/2001/voip/prtcls. htm 10. G. S. Tucker, Voice Over Internet Protocol (VoIP) and Security, SANS Institute (October 2004) 11. Systems Network Attacks Centre (SNAC), Security Guidance for Deploying IP Telephony Systems, NSA (February 2006) 20 CCIP INFORMATION NOTE - ISSUE 06
  21. 21. DISCLAIMER INFORMATION While this publication is accurate to the best of our knowledge, CCIP does not accept any responsibility for errors or omissions. CCIP will not be liable for any loss or damage howsoever caused, arising from or in connection with the use of information contained in this publication. Reference in this publication in any manner to any commercial product, process or service does not constitute or imply its endorsement or recommendation by CCIP. Views and opinions expressed herein may not be used for advertising or product endorsement purposes.
  22. 22. CENTRE for CRITICAL INFRASTRUCTURE PROTECTION www.ccip.govt.nz | ph: +64 4 498-7654 | fax: +64 4 498-7655 PO Box 12-209, Wellington , New Zealand