SPAM prevention in Voice over IP networks via security policies and audio CAPTCHA PhD Thesis Yannis Soupionis Department of Informatics, Athens University of Economics and Business July 4, 2011
Outline 2 Introduction Spam over Internet Telephony (SPIT) Session Initiation protocol (SIP) Security policy CAPTCHA Formal Verification Methodology Research approach Security policy CAPTCHA System architecture - Modules Formal Verification & Experimental Evaluation Contribution & Further research
Introduction Methodology Research contribution Security policy Spam over Internet Telephony (SPIT) CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 3 Bulk unsolicited set of sessions Call initiations Instant messages Presence requests Πηγή : Rosenberg J., Jennings C., The Session Initiation Protocol (SIP) and Spam, Technical Report RFC 5039, Network Working Group, January 2008
Introduction Methodology Research contribution Session Initiation Protocol Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 4 An application-layer control (signaling) protocol for multimedia sessions Initiation Modification Termination Πηγή : J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler, Session Initiation Protocol (SIP), RFC 3261, June, 2002
Introduction Methodology Research contribution SPIT Phenomenon Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 5 Implementation of mechanisms for tackling SPIT attacks by well-known companies as NEC and Microsoft. Recorded SPIT attacks 4 million spam texts sent every day - telegraph.co.uk Stop Spam And Unwanted Calls - cbsnews.com Environmental burden due to SPAM/SPIT Carbon Footprint of Spam ≈ 3 million cars - thegreenitreview.com – McAfee Economic benefits for SPAM response rates ≈ 0,00001% - ACM CCS 2008
Introduction Methodology Research contribution Research approach Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 6 Composing security policy for handling SPIT phenomenon Identification and evaluation of audio CAPTCHA Implementing an original audio CAPTCHA Design of the proposed mechanism architecture Implementation (adaptive) Formal Verification Security policy mechanism Policy integration into VoIP protocol
Introduction Methodology Research contribution Security Policy Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 7 A set of rules or regulations, which has been introduced by the system owner and is related to maintaining an acceptable level of the system security Standards Procedures Guidelines The proposed policy is automated It works as an electronic/web service Πηγή : Γκρίτηαλθσ Δ. Αςφάλεια ςτισ Τεχνολογίεσ Πλθροφοριϊν & Επικοινωνιϊν: Εννοιολογικι κεμελίωςθ, Τμιμα Πλθροφορικισ, Οικονομικό Πανεπιςτιμιο Ακθνϊν
Introduction Methodology Research contribution CAPTCHA Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 8 Completely Automated Public Tests to tell Computers and Humans Apart CAPTCHA categories: Visual: Text or images Audio : Spoken characters Logical : Simple questions We have a natural mother and her daughter. Who is younger? Πηγή : L. Ahn, M. Blum, J. Langford, "Telling humans and computers apart automatically", Communications of the ACM , p. 56-60, Vol. 47 I. 2, February 2004
Introduction Methodology Research contribution Formal methods Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 9 Formal Methods refers to mathematically rigorous techniques and tools for the specification, design and verification of software and hardware systems Intel Pentium (1994) -> a floating point unit flaw, contained in the (60-100MHz) Pentium processors -> Cost: 400 million $ Πηγζσ : Edmund Clarke, Allen Emerson, and Joseph Sifakis, "Model Checking: Algorithmic Verification and Debugging", ACM 2007 Turing Award INTEL FDIV Replacement Program ,California., December, 1994 (http://www.intel.com/support/processors/pentium/fdiv/)
Introduction Methodology Research contribution Methodology Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 10 INVITE INVITE ACCEPT REJECT REJECT CAPTCHA PUZZLE HELP!!! RESULT
Introduction Methodology Research contribution Methodology Security policy CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 11 Implementation Theoretical XML Policy Step Step Detection Module Schema Condition & Event Module Countermeasures CAPTCHA Module Attack Scenarios Monitor Module Identified SPIT Threats Enforcement Module Formal Verification & Experimental Evaluation Adaptive anti-SPIT Policy Framework (ASPF)
Introduction Methodology Research contribution Security policy Vulnerability Classification CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 12 •“Anonymous” in From field Impersonation • Sequential requests for registering and altering to registrar Routing altering & Error • Handling messages with code 301 Silencing • Handling messages with code 403 • Handling responses to messages code 300 Information Drilling • Use of Allow , Suspend and Supported fields • Display-name field Immediate SPIT Threats • Alert-Info and Call-Info fields
Introduction Methodology Research contribution Security policy Attack Scenario CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 13
Introduction Methodology Research contribution Security policy SPIT Attack Graph CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 14 Node Description Find and collect users’ Find and collect users’ 1 1 addresses addresses 2 Send bulk messages Proxies-in-the-middle 3 attack 4 Maximize profit Hide identity-track when Hide identity-track when 5 5 setting-up an attack setting-up an attack Hide identity-track when 6 sending a SPIT call/message Encapsulate SPIT in SIP Encapsulate SPIT in SIP 7 7 messages messages
Introduction Methodology Research contribution Security policy Policy Element / Rule CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 15 The caller’s user agent receives a response with a 300 message Scenario /code (Multiple Choices), which includes a new address in Contact field Attribute Sub-condition Message 300 Code=300 Condition Code=300 Contact One Attribute Sub-condition Contact Field Contact One New SIP address
Introduction Methodology Research contribution Security policy Policy Element / Rule (2) CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 16 Condition Code=300 Contact One 𝐷𝑝𝑜𝑒𝑗𝑢𝑗𝑝𝑜 = 𝑔 𝑑 1 , 𝑑 2 , … , 𝑑 𝑙 = 𝑑 1 ⋄ 𝑑 2 ⋄ ⋯ ⋄ 𝑑 𝑙 , where c i sub-condition and ⋄ logical operator Suggested Countermeasures 1. The UAC uses the specific address to compose upcoming messages 2. The UAC renews the entries for the specific UAS 3. User is informed for the new SIP addresses. 4. The UAC rejects the call and returns a Message 403 (Forbidden) 5. The UAC rejects the call and returns a message 606 (Not Acceptable) 6. The UAC forwards SIP message to another entity and returns a message 183 (Session in Progress )
Introduction Methodology Research contribution Security policy anti-SPIT Policy Creation CAPTCHA Architecture & Modules Verification & Evaluation Contribution & Further research 17 Attribute Sub-condition Policy Instance Attack . . . . . . SPIT scenario condition Policy Element Attribute Sub-condition . . . Set of attack scenarios Policy Element Attribute Sub-condition condition + SPIT Applied Attack SPIT . . . . . . action scenario condition Attribute Sub-condition Policy Element Set of SIP . . . response Suggested messages Countermeasures Block Policy Element Notify Policy Element Notification method Πηγή : Y. Soupionis, S. Dritsas, D. Gritzalis, "An adaptive policy-based approach to SPIT management", in Proc. of the 13th European Symposium on Research in Computer Security (ESORICS 2008), Lopez J., Jajodia S. (Eds.), pp. 446-460, Springer, Malaga, October 2008.
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