On Spam over Internet Telephony
(SPIT)
Prevention

SPIT is defined as the transmission of unsolicited
calls over Internet telephony

Using Internet telephony, these costs...

minimize the probability of blocking legitimate
call

maximize the probability of blocking SPIT calls.

minimize the i...

No Interactions With
Call

Caller-side Interactions

Callee Interrupted by
Call

Callee Receives Call

Feedback From...
Lists

simple mechanism

white lists (identities allowed to call)

black lists (identities that should be rejected)

m...
Circles of Trust
introducing trusted inter-domain connections
each domain controls its own users and the
domains agree not...
Pattern/Anomaly Detection
detecting suspicious patterns in VoIP traffic to
identify SPIT calls
very general
deciding, base...
Greylisting
first call from an unknown user is rejected
Computational Puzzle

giving the caller's terminal a resource
consuming task to perform before establishing
the call

at...
Sender Check

verify that a caller is a valid sender for the
domain from which he is calling.
Turing Test

conversationa...
Consent-based Communication

user A authorize user B, the first time user B tries
to contact user A

it solves the first...
Content Filtering

blocking email spam is essentially based on
content analysis

cannot be fully applied to prevent SPIT...
Reputation System
 attaching reputation score to a contact
 this score can be evaluated based on user
feedback
 it coul...
Limited-Use Addresses
 changing the address as soon as the first
spam messages arrive at the address
 new address has to...
Payments At Risk
 charging a fee for the first contact
 refunding that fee if the call was not SPIT
Legal Action
 intro...
First-Contact Feedback
 the user can provide a feedback to the server
 an unknown identity is allowed to call exactly
on...
 we used a modular design for our prevention
system that flexibly allows linking stages and uses
a modular approach for s...
SPIT PREVENTION AT STAGE 1

All modules examine incoming call signaling and
produce a score

compared to two threshold a...
SPIT PREVENTION AT STAGE 2

If the test is successfully passed ,the
dispatcher forwards the call to the original
callee
...
SPIT PREVENTION AT STAGE 5

Software client allows user to terminate the call
• time indicates to the SPIT prevention sys...
 A systematic classification and reference model
for SPIT prevention building blocks
 Has a purpose of helping newcomers...
 Juergen Quittek & Savario Niccolini; On Spam
over Internet Telephony(SPIT) Prevention, IEEE
Communication magazine, Augu...
THANK YOU
Spit ppt
Spit ppt
Spit ppt
Spit ppt
Spit ppt
Spit ppt
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Spam over Internet Telephony
A systematic classification and reference model for SPIT prevention building blocks
Has a purpose of helping newcomers and practitioners in the area to improve their understanding, and better design and implement SPIT prevention systems

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  • INTRODUCTION
  • Spit ppt

    1. 1. On Spam over Internet Telephony (SPIT) Prevention
    2. 2.  SPIT is defined as the transmission of unsolicited calls over Internet telephony  Using Internet telephony, these costs are substantially lower  presents a reference model for SPIT prevention systems and provides a classification for a large set of available prevention methods
    3. 3.  minimize the probability of blocking legitimate call  maximize the probability of blocking SPIT calls.  minimize the interactions with the callee  limit the inconvenience caused to the caller that tries to place a legitimate call  should be general  should be flexible
    4. 4.  No Interactions With Call  Caller-side Interactions  Callee Interrupted by Call  Callee Receives Call  Feedback From Callee After call
    5. 5. Lists  simple mechanism  white lists (identities allowed to call)  black lists (identities that should be rejected)  members of white lists and black lists may be configured
    6. 6. Circles of Trust introducing trusted inter-domain connections each domain controls its own users and the domains agree not to send SPIT to each other can be implemented in SIP by using authenticated TLS connections between domains
    7. 7. Pattern/Anomaly Detection detecting suspicious patterns in VoIP traffic to identify SPIT calls very general deciding, based on patterns and signatures whether the incoming call might be SPIT or not
    8. 8. Greylisting first call from an unknown user is rejected
    9. 9. Computational Puzzle  giving the caller's terminal a resource consuming task to perform before establishing the call  attackers use botnets to distribute the cost of computing puzzles  limits the effectiveness of the solution
    10. 10. Sender Check  verify that a caller is a valid sender for the domain from which he is calling. Turing Test  conversational method to tell humans and computers  the judge is a human being  most CAPTCHAs are visual although audio CAPTCHAs exist as well
    11. 11. Consent-based Communication  user A authorize user B, the first time user B tries to contact user A  it solves the first-contact problem but introduces a delay until the first call can be placed
    12. 12. Content Filtering  blocking email spam is essentially based on content analysis  cannot be fully applied to prevent SPIT  the receiver has been disturbed by a ringing phone
    13. 13. Reputation System  attaching reputation score to a contact  this score can be evaluated based on user feedback  it could also be tied to other methods
    14. 14. Limited-Use Addresses  changing the address as soon as the first spam messages arrive at the address  new address has to be communicated to all contacts  new user has to be able to get the current address of a recipient
    15. 15. Payments At Risk  charging a fee for the first contact  refunding that fee if the call was not SPIT Legal Action  introducing legislation in all countries to prohibit the distribution of spam over VoIP  there will always be countries where it is legal to send SPIT
    16. 16. First-Contact Feedback  the user can provide a feedback to the server  an unknown identity is allowed to call exactly once and then the callee has to provide a feedback  there is no first-contact problem
    17. 17.  we used a modular design for our prevention system that flexibly allows linking stages and uses a modular approach for stages 1 and 2.
    18. 18. SPIT PREVENTION AT STAGE 1  All modules examine incoming call signaling and produce a score  compared to two threshold a low and a high  below the lower threshold, the call is forwarded to the calee  between the lower and higher thresholds, call is forwarded to the second stage modulesrejected or forwarded to a voicemail system  above the higher threshold, either the call is
    19. 19. SPIT PREVENTION AT STAGE 2  If the test is successfully passed ,the dispatcher forwards the call to the original callee  stage 2 module belonging to the“Turing Test”  based on the assumption that human conversation follows certain activity patterns  sends a prerecorded greeting message
    20. 20. SPIT PREVENTION AT STAGE 5  Software client allows user to terminate the call • time indicates to the SPIT prevention system that this was SPIT  white/black list module may add the caller identity to the black list.
    21. 21.  A systematic classification and reference model for SPIT prevention building blocks  Has a purpose of helping newcomers and practitioners in the area to improve their understanding, and better design and implement SPIT prevention systems
    22. 22.  Juergen Quittek & Savario Niccolini; On Spam over Internet Telephony(SPIT) Prevention, IEEE Communication magazine, August 2008  www.2dix.com
    23. 23. THANK YOU

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