Introduction to VoIP security

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Introduction to VoIP security

• Mark Fawcett, Head of Global Professional
  Services, Aculab

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(No Transcript)
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Session agenda

• Introduction to VoIP security
• Security the basics
• Essential technology and terminology
• Threats and vulnerabilities
• Best practices for VoIP security recommendations

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Session agenda

• Introduction to VoIP security
• Security the basics
• Essential technology and terminology
• Threats and vulnerabilities
• Best practices for VoIP security recommendations

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Introduction to VoIP security

• What do we mean by VoIP security?
• Different things to different people
• Private users, business users, 3rd party
  providers, carriers
• Privacy
• Protection
• Technology

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The state of VoIP security are we in trouble?
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Introduction to VoIP security

• So, were all doomed
• Not really
• Security and fraud are not new
• e-Security is pretty good
• VoIP security is similar
• Were all saved
• Not really
• Poacher vs. gamekeeper
• People will make mistakes
• Time to look in more detail

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Introduction to VoIP security

• What are the real threats?
• Remember, the PSTN isnt secure either
• Before we look at the details, lets start with
  the basics

DoS(Denial of Service) Attacks against call
servers, gateways and other network elements
Eavesdropping Unauthorised call capture, either
internally or externally Includes remote
speakerphone activation
Toll fraud Internal misuse or external access to
call services Rogue call placement
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Session agenda

• Introduction to VoIP security
• Security the basics
• Essential technology and terminology
• Threats and vulnerabilities
• Best practices for VoIP security recommendations

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Security the basics, 3 principles

• Its all about information (spoken, printed,
  transmitted, etc.)
• Worldwide principles DOD, CESG, Academia

DoS(Denial of Service) Attacks against call
servers, gateways and other network elements
Eavesdropping Unauthorised call capture, either
internally or externally Includes remote
speakerphone activation
Toll fraud Internal misuse or external access to
call services Rogue call placement
Integrity Who, what, where, when
Availability When it absolutely, positively has
to be there
Confidentiality Only those who need to know
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Security the basics, threat assessment

• So, we have the 3 tenets
• Confidentiality
• Integrity
• Availability
• But how do we apply them?
• Threat assessment
• Ask a number of questions
• Specific to the requirement
• Relate them to the 3 tenets
• Always think consequences

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Security the basics, threat assessment

• The wrong questions
• Can I be overheard or recorded?
• Am I talking to who I think Im talking to?
• Can I get through when I need to?
• The right questions
• What am I trying to protect?
• What could happen if I cant get through?
• What information could be compromised if Im
  recorded?
• What are the costs to my business of toll-fraud /
  DoS?
• What are the real and important consequences?

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Consequences

• Depends on circumstance
• Consider monitoring of VoIP
• On the Internet
• Joe Public worried about credit card details
  little threat
• Terrorist worried about being monitored big
  threat
• On a private business LAN
• Secure premises, no wireless little threat
• Open premises/access, aggressive competitors
  high threat

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Consequences a question of balance

• If you focus on Confidentiality
• Its to the detriment of Integrity and
  Availability
• What-ifs and backup plans get forgotten
• Example ACME holding corp.
• Need secure communications so all comms are
  secured
• Systems comms keys expire 1st Jan
• No sys-admin on duty
• No fallback in place
• No communications at all

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Security the basics, some truisms

• Security is a form of risk management
• Security through obscurity is not security
• A chain is only as strong as its weakest link
• Nothing is 100 certain
• except death
• ...and taxes

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Session agenda

• Introduction to VoIP security
• Security the basics
• Essential technology and terminology
• Threats and vulnerabilities
• Best practices for VoIP security recommendations

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Encryption

• Think of locking a valuable in a safe with a
  padlock and key
• The valuable is your data
• The padlock is the algorithm
• The key isthe key
• There are two main types of lock and key

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Encryption

• Symmetric
• Basic, strong, padlock
• 2 copies of the same key
• AES, DES
• Asymmetric
• Complex strong padlock
• 2 different key holes
• 2 different keys
• Diffie-Hellman, RSA

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A word of warning
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Symmetric

• Uses a single key to lock/unlock the padlock
• The algorithm (padlock) can come in a variety of
  forms
• Some are more complex than others
• All are fast (lightweight)
• Lots of different modes

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Asymmetric

• Uses one key to lock the padlock, the other to
  unlock it
• The padlock is very complicated
• Hows your prime number and factoring
  mathematics?
• The algorithms are slow
• How does it work in practice?
• Keys come in pairs, public/private
• I publish (or send you) my public key
• You write something
• You encrypt (lock) it using my public key
• I (and only I) can decrypt (unlock) it using my
  private key

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To summarise

• Symmetric
• Good, strong but basic padlock
• Needs copies of the same key vulnerable to
  compromise
• Fast
• Asymmetric
• Good, strong and complex padlock
• Uses different keys much less vulnerable to
  compromise
• Slow

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How to make this work for VoIP

• Need a fast encryption/decryption algorithm for
  RTP comms
• Symmetric (AES etc.)
• Relies on a shared, common, key
• Change the key regularly - how to exchange it
  securely?
• Symmetric keys are typically short (in comparison
  to traffic)
• We need a reliable, secure exchange mechanism
• Does not need to be fast (real-time)
• So we can use asymmetric algorithm to exchange
  keys
• we have the power

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VoIP security essential technology and
terminology

• ..we have the power, are we ready for some terms
• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

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VoIP security essential technology and
terminology

• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

• Transport Layer Security (TLS)
• - Cryptographic protocol for Internet
  applications (supersedes SSL)
• TLS involves three basic phases
• Peer negotiation for algorithm support
• Key exchange and authentication (RSA,
  Diffie-Hellman, etc.)
• Message encryption and authentication (Symmetric
  ciphers Triple DES, AES Cryptographic hash
  function HMAC-MD5 or HMAC-SHA )

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VoIP security essential technology and
terminology

• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

• Secure RTP (IETF RFC 3711)
• Encryption (confidentiality)
• Authentication (message integrity)
• Anti-replay protection
• Used for voice and video
• Supports both unicast and multicast
• No key management mechanism
• Utilised only one cipher (AES)

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VoIP security essential technology and
terminology

• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

• Secure SIP (SIP with TLS)
• Requires support for SIP over TCP (still part of
  the IETF RFC 3261)
• - Protects SIP messages against
• Encryption (confidentiality)
• Authentication (message integrity)
• Anti-replay protection
• Integrated key management with mutual
  authentication and secure key distribution
• Applied between proxies or UA/proxy

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VoIP security essential technology and
terminology

• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

• IPsec secure form of IP tunnelling
• Encryption (confidentiality)
• Authentication (message integrity)
• Anti-replay protection
• - Operates at the network layer (OSI L3) while
  TLS, SRTP, SIPS _at_ OSI L4-L7
• Mainly used for VPN communications
• Mandatory security scheme for IPv6
• Two operation modes
• Transport (message body encryption)
• Tunnel (whole packet)

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VoIP security essential technology and
terminology

• MIKEY Key management procedure
• - Negotiation of cryptographic keys and security
  parameters (SP)
• Multimedia Internet KEYing (IETF RFC 3830)
• Designed for real time traffic (SIP/RTP calls,
  RTSP, streaming, groups, multicast)
• Single or multiple crypto sessions (RTP/RTCP
  encrypted separately)
• Symmetric key distribution (pre-shared keys,
  HMAC integrity protection)
• Asymmetric key distribution
• Diffie-Hellman key agreement protected by
  digital signatures

• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

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VoIP security essential technology and
terminology

• HMAC keyed-Hash Message Authentication Code
• - Verifies data integrity and authenticity of
  a message
• IETF RFC 2202
• SHA-1 and MD5 are two main types of
  cryptographic hash functions
• Operate on 512-bit blocks
• Cryptographic strength depends on the hash
  functions

• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5

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VoIP security essential technology and
terminology

• We have looked at
• TLS
• Secure RTP (SRTP)
• SIPS
• IPsec
• MIKEY
• HMAC SHA-1 / MD5
• we have even more power

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Session agenda

• Introduction to VoIP security
• Security the basics
• Essential technology and terminology
• Threats and vulnerabilities
• Best practices for VoIP security recommendations

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SIP specific vulnerabilities

• Eavesdropping
• General/directory scanning
• Flooding/Fuzzing
• Registration highjack/manipulation
• Man-in-the-middle

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SIP specific vulnerabilities

• Session tear-down
• Reboot attacks
• Redirection
• RTP
• SPIT
• Vishing

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What does it all mean?

• Confused, uncertain?
• You are not alone, what does it all mean?

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What does it all mean an opinion

• The reality business
• VoIP deployments are growing, security is keeping
  pace
• Large scale VoIP is being deployed within
  business LANs
• PSTN provides a firebreak
• Firewalls/SBCs can provide IP firebreaks
• The reality private users
• VoIP is used over the Internet (or on connected
  systems)
• Tend to be on soft devices
• More vulnerable to attack and compromise
• Used as a vector to gain remote access

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What does it all mean an opinion

• The reality third party carriers
• Huge amount of cheap call providers
• Often use VoIP for long-haul/international legs
• What is that VoIP being carried over?
• How vulnerable are those links?

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What does it all mean an opinion

• The reality tier 1 and 2 carriers
• ATT, BT et al. moving to IP core networks
• Does this mean IP/SIP all the way for voice?
• Does this mean end-end security will be provided?
• Does this mean end-end security could be added by
  user?
• Will an IP carrier look anything like a current,
  Internet/LAN call?

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Session agenda

• Introduction to VoIP security
• Security the basics
• Essential technology and terminology
• Threats and vulnerabilities
• Best practices for VoIP security recommendations

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Recommendations

• KISS
• Dont just install products
• Audit and trace
• Apply updates
• Test and attack
• Holistic approach

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Recommendations

• Separate voice and data on different networks
• Logical or physical
• Different subnets (address blocks) for voice and
  data traffic
• Apply call control security - SIPS
• Additionally apply voice traffic security (SRTP)
• Secure access
• Remote administration of network devices
• WPA not WEP for wireless

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Recommendations - additional

• Border controls
• Use protocol breaks
• Allow VoIP traffic via an intelligent firewall
• Dont rely on firewall bypass protocols/techniques
  (STUN etc.)
• Stateful packet rules and filtering
• Avoid soft-phones if possible
• Session Border Controllers can be used

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Sample network architecture
Separate VoIP and data logical/physical subnets
SecureRTP and SIPS are applied
VoIP calls pass via the firewall (STUN, TURN, ICE)
SIP and RTP are disallowed, OAMP is via IPsec or
SSH
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Any questions?
Have you got any questions?
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Summary

• Security Confidentiality, Integrity and
  Availability
• Consequences and threat assessments
• VoIP security threats are real
• The risks are not new or unique to VoIP
• There are several steps that can mitigate/manage
  threats
• Carriers moving to VoIP cores is a different
  issue
• Essential technology TLS, Secure RTP, SIPS,
  IPsec, MIKEY

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Thank you

• mark.fawcett_at_aculab.com