1. A Survey of VoIP Security Practices in Higher Education
Network Security Effective Practices - VoIP: SIP, H.323
A Survey of VoIP Security Practices in Higher Education
H. Morrow Long
Director, Information Security
Yale University
Educause 2007 Annual Conference Session
Wednesday, October 24, :30 a.m. - 12:45 p.m.
8:00 a.m. Registration
8:30 a.m. Introduction and Overview to Seminar
9:00 a.m. Creating a Security Risk-Aware Culture
9:30 a.m. Defining Institutional Data Types
10:15 a.m. Break
10:30 a.m. Reducing Access to Data Not Absolutely Essential
Noon Lunch
1:00 p.m. Establishing and Implementing Stricter Controls
2:00 p.m. Providing Awareness and Training
2:30 p.m. Verifying Compliance
2:45 p.m. Break
3:00 p.m. Putting it All Together:  Moving from Planning to Action
4:00 p.m. Wrap-Up
4:30 p.m. Adjourn

2. Introductions
Krizi will bring BINGO sheets and light-up bouncy balls as a prize
5 minutes to go over the implications of the BINGO categories
Flip Chart the type of functions
Flip Chart what folks want to get out of the session

3. Overview
This presentation will discuss a survey and informal poll of the current campus network VoIP security practices and products in higher education on both wired and wireless networks.

4. Agenda Introduction What is VoIP? VoIP Threats
VoIP Security Checklists
VoIP Effective Practices in Higher Ed
Survey of VoIP Security in Academia
Discussion and Questions

5. VoIP Security Goes Mainstream
In 2006, VoIP Security entered the SANS Top 20 for the first time:
N1 VoIP Servers and Phones

6. VoIP Security Flaws Go Mainstream
2006 VoIP Security vulnerabilities:
Asterisk CVE , CVE , CVE , CVE
Cisco Call Manager CVE , CVE
VoIP Phones CVE , CVE , CVE , CVE , CVE , CVE , CVE

7. VoIP Security Flaws Go Mainstream
2007 VoIP Security vulnerabilities:
Asterisk CVE
Cisco Call Manager / IOS / PIXOS CVE , SA24180/cisco-sa fwsm, SA24179/cisco-sa pix
VoIP Phones CVE , CVE , CVE

8. What is VoIP? Voice over IP IP Telephony
Converged Data/Voice Networking
Unified Messaging

9. What is VoIP? 2 Major Protocols: Popular Internet VoIP Other
SIP / SIPS
Popular Internet VoIP
Proprietary
Skype
Vonage
Other
Zfone/ZRTP (Phil Zimmerman)
Internet Standards related to VoIP Security:
IPSEC
SSL/TLS
SRTP (RFC3711)

10. H.323 and SIP The 2 Major (Local and Enterprise) VoIP Protocols:
Both protocols:
Are hard (but not impossible) to firewall
Were not designed for security…
Use separate signaling and media (content) channels
Use dynamic ports
Were not designed to be NAT “friendly” (embed IP addresses inside signaling/control information)
But: H.323 is more like ISO X. protocols (uses ASN.1/PER) and SIP is more like Internet FTP/SMTP/HTTP/NNTP.

11. H.323 Older protocol than SIP, implemented earlier
ITU Umbrella Standard - built of other H stds
First VoIP std to use RTP
Interoperates with ISDN PBX systems
Used by several voice and videoconferencing systems
Built into NetMeeting, other commercial and open source programs available
GNU Gatekeeper - accounting/authorization/NAT traversal/H.323 proxy/H.235 security

12. H.235 Security H.235 provides security for H.323
Optionally nine security profiles can be used to apply one or more of six security services (authentication, nonrepudiation, integrity, confidentiality, access control, key management) to H.225, H.245 and RTP traffic.

13. “Skinny” - Cisco H.323
“Skinny” is Cisco’s lightweight proprietary version of H.3323.
SCCP is the acronym for Skinny Client Control Protocol.
It is a lower overhead control protocol between the client and Call Manager.

14. SIP - Session Initiation Protocol
Overtaking H.323 on LANS - many clients.
Created SIP 2.0 defined in RFC 2543 (1999)-- refined in RFC 3261 (2002).
Lightweight, text-based protocol run on top of UDP or TCP (e.g. port mod P2P model.
Uses HTTP “style” status codes & addresses.
Interoperates with XMPP IM (Japper)
STUN & newer TURN enable SIP through NAT using public Internet servers.
Uses other protocols: SDR, RTP, MGCP, RTSP.
Can be stateful/less, client/server or P2P.

15. SIP/RTP Architecture VoIP User-Agent RTP SIP SRTP TLS UDP and TCP IP
Data Link Layer
Credit: Practical VoIP Security, Syngress

16. SIPS - Secure SIP Secure SIP is a security mechanism defined by SIP
RFC 3261 (2002) defines Secure SIP -- a security mechanism using TLS to send SIP messages over an (Transport Layer Security) encrypted channel.
Fairly new, competes with IPSEC, VPNs, SRTP -- often referred to as SIP with TLS -- used when IPSEC is overkill or SIP proxies must be used.

17. SRTP
Adds message encryption, authentication, integrity and replay protection to to RTP
Sister to SRTCP (Secure RTP Control Proto)
SRTP/SRTCP encryption, authentication and integrity are independent and can be disabled (“Null” encryption).
Single Cipher (AES), 2 modes (counter & feedback modes)
External Key mgt (ZRTP, Mikey, …)
Credit:

18. SRTP Interoperability
Hard IP Phones
Avaya, Cisco, Ericsson (&TLS), Siemens, Linksys, Snom (&TLS)
Soft IP phones
Gizmo, Kphone, Snom360 (&TLS), minisip (&TLS)
Hard IP PBX - Alcatel and Ericsson
Soft-IP-PBX - Asterisk (SIP & H323) and pbxnsip
SBC (Session Border Ctrlr) / SIP Firewall
Covergence (& SIP & H323)
InGate (SIP aware firewall)
Credit:

19. Zfone/ZRTP Created/driven by (Phil Zimmerman) 2nd attempt (PGPfhone)
Designed to work with current SIP phone programs (via plug-ins).
Zfone is the program.
ZRTP is an extension to RTP (Real-time Transport Protocol) providing secure real-time transport to secure sessions (SIP, H.323, etc.) already established.
Keys are transmitted and managed outside the std signaling.
Protection against MitM (man in the Middle) attacks.

20. Skype Peer to Peer Model Supernodes route traffic for other calls
Can be blocked and bandwidth managed
Outlawed at some institutions
Proprietary strong encryption
Non-CALEA compliance?

21. More VoIP Terminology “Presence” (R U there?)
Convergence (Data + Voice = Synergy)
Voice Messaging
Unified Messaging Systems

22. More VoIP Acronyms ACD Automatic Call Distribution(Call Ctr)
IVR Interactive Voice Response
ICE Interactive Connectivity Establishment
RSVP Resource Reservation Protocol
RTSP Real Time Streaming Protocol
SDP Session Discovery Protocol
STUN Simple Traversal of UDP through NAT
TLS Transport Layer Security (ala SSLv3)
TURN Traversal Using Relay NAT
TTS Text-to-speech server

23. Non-Cyber Security-related VoIP Issues
911 - where does 911 ring?
E need to provide location information?
Emergency access -
during network or power outages
Use Power-over-Ethernet (PoE AKA IEEE 802.3af) cabling
Provide at least the minimal # of land lines per # rooms (e.g. or as required by law)

24. PBX System Components PSTN Endpoints (Phones, Faxes, Modems.)
Lines (e.g. Station lines)
Trunks
Remote PBXes
Adjuncts (VM, ACD, IVR, …)
CDR (Call Detail Recording)
Voice/PBX Firewalls

25. VoIP System Components
Media Gateways -- e.g. to PSTN/PBXes
Endpoints (User Agents): softphones, IM/Video/VoIP/ATA (Analog Telephone Adatper)
Media Servers (VM, ACD, IVR, TTS,VC)
H.323 Gatekeepers
SIP Registration, Redirect Servers
SIP Proxy Servers
Firewalls/ALGs

26. VoIP Threats
VoIP Networks have many of the same threats to security, privacy and reliability as data networks do, but they also bring in the problems of the telephone system and have some special threats all their own.
Converged networks can combine threats from the data and VoIP world -- making the new network less secure (in the opinion of some).
Data network people are afraid VoIP infrastrucutre will weaken the security of their data network and the voice/telecom people feel the same about data / IP networks.

27. Other VoIP Architectures
Skype
IAX
H.248
Microsoft Live Communication Server 2005 (MLCS)
TLS between client and server
Mutual TLS server-to-server

28. VoIP vs. PSTN
Remember that “POTS” telephones have little security -- ordinary phone conversations are not encrypted and can be tapped or eavesdropped.
You can actually have better security using VoIP IF you use strong encryption (and a good implementation).

29. VoIP Threats DDoS / DoS Attacks Unauthorized Access Toll Fraud
ICMP Flood (eg ‘pings’) to Phone or Call Mgr
Unauthorized Access
Toll Fraud
Voic hacking
Eavesdropping (Call and/or Control)
Call Hijacking
Application Level Attacks
Credit: Juniper Networks

30. IP Network Threats Ethernet, IP and DNS address spoofing
ARP and DNS Cache Poisoning
Quantity-based packet flooding
Stack DoS attacks
VLAN “jumping”
QoS / prioritization attacks

31. Organizing VoIP Threats
Standard IP Network Threats
(to the CIA triad)
C - Confidentiality
I - Integrity
A - Availability

32. Organizing VoIP Threats
Advanced IP Network Issues/challenges
(triple A)
A - Authentication
A - Authorization
A - Accounting

33. Application-Specific VoIP Threats
“Phone” spoofing - registering a SIP client with someone else's identifier (no auth.).
a successful attack would cause the similarly registered phone to ring when someone called the legitimate owner of the number.
Credit: Jeremy George, Yale University

34. Threat to Confidentiality
Programs exist to listen to SIP and other VoIP streams (and record them).
It is possible to capture packets on switched networks (by overflowing ARP tables, poisoning ARP caches, etc.).
Encryption should be used but has side- effects: : on latency, on sound qulaity (packetization and compression chunking can lead to clipped staccato speech).

35. Application-Specific VoIP Threats
Caller-ID / ANI “Spoofing” (faking source #)
Trivial to do -- don’t trust Caller-ID -- OK to screen w/
Credit: Jeremy George, Yale University

36. Threat to Integrity It is possible to ‘hijack’ sessions.
It is possible to modify voice over IP streams.
Once again, use encryption (or at least cryptographic integrity checks) to prevent this.

37. Application-Specific VoIP Threats
MitM “spoofing”
CALEA is a ‘legit’ application of this.
DoS attacks are known immediately by communicating parties
Call content is neither overheard nor compromised.
Some proxies have logic in them that identifies a likely DoS attack and discard those packets (ask your vendor!).
Encryption is the best proection against MitM spoofing.
Credit: Jeremy George, Yale University

38. Threats to Availability
Quality of Service (QoS) problems:
Latency - time for traffic to go from source to destination (one-way and round-trip). 150ms is Max RTT for PSTN. VoIP at 400ms is at outer limit of tolerable range.
Jitter - variability in latency and out-of-order packet arrival times. Buffering can help here.
Packet Loss - results in gaps in communication.

39. Application-Specific VoIP Threats
“Special DoS (Denial of Service) attacks
high volume flood of SIP INVITEs
high volume flood of SIP REGISTER commands
Control Packet / Call Data Floods
Packet Replay / Injection / Modification
Credit: Jeremy George, Yale University

40. Application-Specific VoIP Threats
“BID attacks on SIPS”
Get SIPS devices to downgrade to ordinary SIP
Credit: Jeremy George, Yale University

41. Application-Specific VoIP Threats
Rogue SIP Proxies
Impersonate a proxy to a User-Agent
Credit: Practical VoIP Security, Syngress

42. VoIP Security Checklist
Practical VoIP Security “high level short list”:
Create, publish and enforce security policies.
Practice rigorous physical security.
Verify user identities.
Actively monitor logs, firewalls & IDSes.
Logically segregate data & voice traffic.
Harden Oses.
Encrypt whenever and whatever you can.

43. VoIP Security Checklist
Juniper Best Pracices Security Measures
1. Maintain Current Patch Levels
2. Install a Good Anti-Virus System and Update it Regularly
3. Apply State-of-the-Art Intrusion Detection and Prevention Systems
4. Install Application-Layer Gateways between Trusted and Untrusted Zones.
5. Enforce SIP security by means of Authentication, Authorization and IPSec
6. Establish Policy-Based Security Zones to Isolate VoIP Segments.
7. Run VoIP Traffic on VPNs to Minimize Eavesdropping Risk on Critical Segments.
8. Use VLANs to Prioritize and Protect Voice Traffic from Data Network Attacks
9. Apply Encryption Selectively
10 Protect Against UDP Flooding
11. Develop a Holistic Security Program

44. Meta Group Checklist IP Telephony-Specific Security Features
The Call Control Server
Harden/Strip down OS.
Use secure OS.
Authenticate & authorize all user & device access to servers.
Require strong authentication for all configuration and software upgrades.
Should support app level signaling message auth.
Should support call setup info encryption.

45. Meta Group Checklist IP Telephony-Specific Security Features
The Voice Gateway:
Require strong authentication for all configuration and software upgrades .
Provide DoS protection on IP inteface.
Should be configured to route calls only via the call control server.
Secure OS w/anti-virus AND host-based IDS.
Should support call setup info and media (voice content) encryption.
Should support a media (voice content) protocol authentication on a per-packet basis.

46. Meta Group Checklist IP Telephony-Specific Security Features
The IP Phone:
Must authenticate itself to the call control server or a proxy server upon initial registration
Must support strong authentication for any remote configuration and software upgrades .
Should support a configurable access control list to control any incoming traffic (e.g. H.323/SIP, RTP, HTTP, FTP, DHCP)..
When supporting an additional Ethernet port for PC connectivity, should have this implemented via a switching function combined with VLAN functionality.
Should support encryption of both call setup info and media as needed. Using encryption can add an additional end-to-end delay on each media packet.

47. VoIP Security Checklist
Detailed and Specfic list:
Use a separate VLAN with 802.1p/q QoS w/priority VLAN tagging for the VoIP network.
Use a private (RFC1918) IP network for the VoIP LAN.
Use NAT and/or proxies to hide internal addresses.
Use a firewall (packet filtering or ALG) to protect & connect the VoIP network to the data IP network.
Use an IDS or IPS to examine the traffic allowed through the firewall (may be built into the firewall).
Use TLS to protect SIP and SRTP to protect RTP.
Use NAC, 802.1X & RADIUS auth & SIP-aware FW.

48. Listservs & Newsgroups
EDUCAUSE Security Discussion Listserv
VOIPSA Best Practices Working Group
VOIPSA Best Practices WG List
NIST Publication Mailing list
NIST
Receive immediate notification when new NIST computer security publications or news are available.
US-CERT
Technical Cyber Security Alerts provide timely information about current security issues, vulnerabilities, and exploits.

49. VoIP Security Effective Practices in Higher Ed
One anonymous school:
Uses separate VLAN, L2 switches and RFC1918 IP addresses for VoIP network.
Provides separate connections (and bandwidth) to each building with VoIP.
Softphones can participate from regular campus LAN (aren’t required to use a 2nd NIC on the VoIP network).

50. VoIP Security Effective Practices in Higher Ed
A 2nd anonymous school:
Has enterprise polycom gateways (a bunch of them) that have priority in QOS on the routers..
Allows traffic via ports inbound on the above routers for this ‘legit’ traffic.
Doesn’t restrict H.323.
Blocks SIP and Vonage because they don’t open the inbound ports.
Packet8 and other SIP applications which use STUN work fine (because of tunneling).
Skype is a problem (paritcularly Supernodes at times).

51. Survey

52. VoIP Higher Ed Security Survey

53. VoIP Higher Ed Security Survey

54. VoIP Higher Ed Security Survey

55. VoIP Higher Ed Security Survey

56. VoIP Higher Ed Security Survey

57. VoIP Higher Ed Security Survey

58. Which VoIP Security mechanisms do[n’t] you use?
VoIP Higher Ed Security Survey
Which VoIP Security mechanisms do[n’t] you use?
Use H.235 for H.323 security profiles (for H.225, H.245 and RTP traffic).
Use SIPS (Secure SIP - RFC SIP over TLS).
Don't allow SRTP with null cipher (e.g. don't allow use of SRTP for just authentication).
Use zRTP for key management.
Use Mikey for key mgt/exchange.
Use SDES for key exchange.
Use SRTCP for authentication.
Use SRTCP for encryption.
IPSEC to secure MGC (Media Gateways/Controllers) communication.
Use of separate physical LAN(s) for VoIP for segregation from data IP network.

59. VoIP Higher Ed Security Survey
Which VoIP Security mechanisms do[n’t] you use?
Use of IPS between VoIP network and data IP network.
Use of IDS between VoIP network and data IP network.
Use NAC (network access control) such as 802.1X and RADIUS to authenticate hard phones.
Softphones require the use of the separate VoIP network (physical LAN, VLAN, subnet address, etc.) from the data IP network.
Softphones are allowed with IPSEC transport mode.
Softphones are allowed with IPSEC VPNs.
Allow NAT traversal via STUN or TURN Internet proxies.
Provide separate dedicated bandwidth for VoIP traffic to the Internet.

60. Survey

61. Wrap-Up
Question & Answer
Session Evaluation & Feedback

62. Contact Info
H. Morrow Long
Security.yale.edu

63. Credits:
Cisco - Configuring SIP High Availability Applications,
Jeremy George, Yale University, “ “SIP.edu Cookbook - Security Considerations”
Deb Shinder, 2006/12/1 “Make a SIP-based VoIP network more secure”,
Deb Shinder, 2007/1/7 “Take a multi-layered approach to VoIP security”,
Jose J. Valdes, Jr., Colorado State University “Voice over Internet Protocol (VoIP) Security”, Conference, ICS – Wireless Group Meeting, Tempe, Arizona, February 6, 2005

64. Credits:
Practical VoIP Security by Larry Chaffin, Jan Kanclirz, Jr., Thomas Porter, Choon Shim, Andy Zmolek, Syngress, March 2006
Wikipedia (pages on H.323, SIP, SRTP, ZRTP), Zfone, etc.)

65. This has been a chalk outline™ production.