IP Library Granted Patent US 12,621,382
Granted Patent B2
US 12,621,382 · App. 18/680,327 · Granted May 5, 2026

Call classification through analysis of DTMF events

Inventors: Nick Gaubitch (Atlanta, GA); Scott Strong (Atlanta, GA); John Cornwell (Atlanta, GA); Hassan Kingravi (Atlanta, GA); David Dewey (Atlanta, GA)
Assignee: Pindrop Security, Inc.
H04M1/56H04L25/0202H04M3/2281H04M3/493H04M7/1295H04Q1/45H04Q3/70G10L25/51H04M2201/18H04M2203/60H04Q2213/13139H04Q2213/13405H04Q2213/13515
View Patent ↗
Loading inventors, assignments & file history…
Monitor This Case
Get email alerts when status or documents change.
Order Certified Copies
Most orders are placed with the USPTO same day — all within 24 business hours.
Order via The Patent Place →
Pre-filled with this patent's details
Quick Facts
Patent No.
US 12,621,382
App. No.
18/680,327
Granted
May 5, 2026
Kind
B2
Abstract

Systems, methods, and computer-readable media for call classification and for training a model for call classification, an example method comprising: receiving DTMF information from a plurality of calls; determining, for each of the calls, a feature vector including statistics based on DTMF information such as DTMF residual signal comprising channel noise and additive noise; training a model for classification; comparing a new call feature vector to the model; predicting a device type and geographic location based on the comparison of the new call feature vector to the model; classifying the call as spoofed or genuine; and authenticating a call or altering an IVR call flow.

Claims (38)

1 . A computer-implemented method comprising:

obtaining, by a computer, via a remote computer dual-tone multi frequency (DTMF) information associated with a new phone call;

generating, by the computer, a new call feature vector for the new phone call using the DTMF information of the new phone call;

determining, by the computer, a fraud probability that the new phone call is fraudulent or genuine, based upon comparing the new call feature vector against one or more prior call feature vectors for one or more prior phone calls, each prior call feature vector generated based upon the DTMF information of a prior phone call corresponding to the prior call feature vector; and

generating, by the computer, a user interface comprising an indicator of the fraud probability for the new phone call.

2 . The method according to claim 1 , further comprising providing, by the computer, the user interface having the fraud probability for display at the remote computer.

3 . The method according to claim 1 , further comprising, for each prior phone call of the one or more prior phone calls, generating, by the computer, the prior call feature vector using the DTMF information for the prior phone call.

4 . The method according to claim 1 , wherein each prior call feature vector is associated with a corresponding label indicating one or more characteristics of the prior phone call corresponding to the prior call feature vector,

the method further comprising training, by the computer, a classifier model according to each of the prior call feature vectors and the associated label for each of the prior phone calls.

5 . The method according to claim 4 , further comprising generating, by the computer, one or more fingerprint models associated with a known caller by executing the classifier model on a set of prior call feature vectors generated using the DTMF information for one or more of prior phone calls associated with the known caller.

6 . The method according to claim 4 , further comprising classifying, by the computer, the new phone call as fraudulent or genuine by applying the classifier model on the new call feature vector generated for the new phone call.

7 . The method according to claim 1 , further comprising generating, by the computer, ideal DTMF information corresponding to the DTMF information received during an Interactive Voice Response (IVR) session of the new phone call,

wherein the computer generates the new call feature vector for the new phone call based upon one or more differences between the ideal DTMF information and the DTMF information of the new phone call.

8 . The method according to claim 7 , further comprising estimating, by the computer, additive noise in the DTMF information of the new phone call based upon the difference between the ideal DTMF information and the DTMF information of the new phone call.

9 . The method according to claim 7 , further comprising estimating, by the computer, channel noise in the DTMF information of the new phone call based upon the difference between the ideal DTMF information and the DTMF information of the new phone call.

10 . The method according to claim 7 , further comprising, for each prior phone call:

generating, by the computer, prior ideal DTMF information corresponding to the prior DTMF information received during a prior IVR session of the prior phone call; and

generating, by the computer, the prior call feature vector for the prior phone call based upon one or more differences between the prior ideal DTMF information and the prior DTMF information of the prior phone call.

11 . A system comprising:

one or more network interfaces configured to receive dual-tone multifrequency (DTMF) information for a plurality of calls associated with a plurality of phone numbers; and

a processor configured to:

obtain via a remote computer the DTMF information associated with a new phone call;

generate a new call feature vector for the new phone call using the DTMF information of the new phone call;

determine a fraud probability that the new phone call is fraudulent or genuine, based upon comparing the new call feature vector against one or more prior call feature vectors for one or more prior phone calls, each prior call feature vector generated based upon the DTMF information of a prior phone call corresponding to the prior call feature vector; and

generate a user interface comprising an indicator of the fraud probability for the new phone call.

12 . The system according to claim 11 , wherein the processor is further configured to provide the user interface having the fraud probability for display at the remote computer.

13 . The system according to claim 11 , wherein the processor is further configured to, for each prior phone call of the one or more prior phone calls, generate the prior call feature vector using the DTMF information for the prior phone call.

14 . The system according to claim 11 , wherein each prior call feature vector is associated with a corresponding label indicating one or more characteristics of the prior phone call corresponding to the prior call feature vector, and

wherein the processor is further configured to train a classifier model according to each of the prior call feature vectors and the associated label for each of the prior phone calls.

15 . The system according to claim 14 , wherein the processor is further configured to generate one or more fingerprint models associated with a known caller by executing the classifier model on a set of prior call feature vectors generated using the DTMF information for one or more of prior phone calls associated with the known caller.

16 . The system according to claim 14 , wherein the processor is further configured to classify the new phone call as fraudulent or genuine by applying the classifier model on the new call feature vector generated for the new phone call.

17 . The system according to claim 11 , wherein the processor is further configured to generate ideal DTMF information corresponding to the DTMF information received during an Interactive Voice Response (IVR) session of the new phone call, and

wherein the computer generates the new call feature vector for the new phone call based upon one or more differences between the ideal DTMF information and the DTMF information of the new phone call.

18 . The system according to claim 17 , wherein the processor is further configured to estimate additive noise in the DTMF information of the new phone call based upon the difference between the ideal DTMF information and the DTMF information of the new phone call.

19 . The system according to claim 17 , wherein the processor is further configured to estimate channel noise in the DTMF information of the new phone call based upon the difference between the ideal DTMF information and the DTMF information of the new phone call.

20 . The system according to claim 17 , wherein the processor is further configured to, for each prior phone call:

generate prior ideal DTMF information corresponding to the prior DTMF information received during a prior IVR session of the prior phone call; and

generate the prior call feature vector for the prior phone call based upon one or more differences between the prior ideal DTMF information and the prior DTMF information of the prior phone call.

Assignments (2)
SECURITY INTEREST Recorded Jun 26, 2024
From: PINDROP SECURITY, INC.
To: HERCULES CAPITAL, INC., AS AGENT
Reel/Frame 067867/0860 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded May 31, 2024
From: GAUBITCH, NICK; STRONG, SCOTT; CORNWELL, JOHN; KINGRAVI, HASSAN; DEWEY, DAVID
To: PINDROP SECURITY, INC.
Reel/Frame 067586/0297 →
Continuity (7)
Continuation 17857618 · Jul 5, 2022
Continuation 17157848 · Jan 25, 2021
Continuation 16378286 · Apr 8, 2019
Continuation 15600625 · May 19, 2017
Provisional Application 62370135 · Aug 2, 2016
Provisional Application 62370122 · Aug 2, 2016
Related Publication 20240323270A1 · Sep 26, 2024
References Cited (46)
US 5442696A · Lindberg et al. · 1995 [cited by applicant]
US 5570412A · Leblanc · 1996 [cited by applicant]
US 5724404A · Garcia et al. · 1998 [cited by applicant]
US 5825871A · Mark · 1998 [cited by applicant]
US 6041116A · Meyers · 2000 [cited by applicant]
US 6134448A · Shoji et al. · 2000 [cited by applicant]
US 6654459B1 · Bala et al. · 2003 [cited by applicant]
US 6735457B1 · Link et al. · 2004 [cited by applicant]
US 6765531B2 · Anderson · 2004 [cited by applicant]
US 7787598B2 · Agapi et al. · 2010 [cited by applicant]
US 8050393B2 · Apple · 2011 [cited by applicant]
US 8223755B2 · Jennings et al. · 2012 [cited by applicant]
US 8311218B2 · Mehmood et al. · 2012 [cited by applicant]
US 8385888B2 · Labrador et al. · 2013 [cited by applicant]
US 9060057B1 · Danis · 2015 [cited by applicant]
US 9078143B2 · Rodriguez et al. · 2015 [cited by applicant]
US 10257591B2 · Gaubitch et al. · 2019 [cited by applicant]
US 10904643B2 · Gaubitch et al. · 2021 [cited by applicant]
US 11388490B2 · Gaubitch et al. · 2022 [cited by applicant]
US 12015731B2 · Gaubitch · 2024 [cited by examiner]
US 20020181448A1 · Uskela et al. · 2002 [cited by applicant]
US 20030012358A1 · Kurtz et al. · 2003 [cited by applicant]
US 20110051905A1 · Maria Poels · 2011 [cited by applicant]
US 20110123008A1 · Sarnowski · 2011 [cited by applicant]
US 20150120027A1 · Cote et al. · 2015 [cited by applicant]
US 20160150414A1 · Flaks et al. · 2016 [cited by applicant]
US 20160293185A1 · Cote et al. · 2016 [cited by applicant]
US 20170222960A1 · Agarwal et al. · 2017 [cited by applicant]
US 20170302794A1 · Spievak et al. · 2017 [cited by applicant]
US 20170359362A1 · Kashi et al. · 2017 [cited by applicant]
Australian Office Action on AU Appl. Ser. No. 2017305245 dated Apr. 28, 2021 (3 pages). [cited by applicant]
Canadian Examination Report dated Oct. 16, 2019, issued in corresponding Canadian Application No. 3,032,807, 3 pages. [cited by applicant]
European Patent Office Office Action on EP Appl. Ser. No. 17752526.8 dated Mar. 31, 2021 (7 pages). [cited by applicant]
Examination Report for CA Appl. Ser. No. 3032807 dated Jul. 2, 2021 (4 pages). [cited by applicant]
Examination Report No. 1 on AU App. Serial No. 2022201831 dated Apr. 4, 2023 (2 pages). [cited by applicant]
Examiner Requisition in Canadian Application No. 3,032,807 dated Jul. 3, 2020 (4 pages). [cited by applicant]
Examiner's Requisition dated Mar. 28, 2024 on CA App. 3,178,322 (4 pages). [cited by applicant]
Final Office Action on U.S. Appl. No. 16/378,286 dated Jun. 9, 2020 (9 pages). [cited by applicant]
International Search Report issued in International Application No. PCT/US2017/044849 dated Jan. 11, 2018 (8 pages). [cited by applicant]
Non-Final Office Action on U.S. Appl. No. 15/600,625 dated Jan. 23, 2018 (16 pages). [cited by applicant]
Non-Final Office Action on U.S. Appl. No. 16/378,286 dated Jan. 17, 2020 (39 pages). [cited by applicant]
Non-Final Office Action on U.S. Appl. No. 17/857,618 dated Oct. 3, 2023 (10 pages). [cited by applicant]
Notice of Allowance issued on U.S. Appl. No. 16/378,286 dated Sep. 24, 2020 (5 pages). [cited by applicant]
Notice of Allowance on U.S. Appl. No. 15/600,625 dated Nov. 13, 2018 (6 pages). [cited by applicant]
Notice of Allowance on U.S. Appl. No. 17/857,618 dated Feb. 15, 2024 (5 pages). [cited by applicant]
Schulzrinne et al., “RTP Payload for DTMF Digits, Telephone Tones, and Telephony Signals” Columbia University, Dec. 2006, (50 Pages)<https://tools.ielf.org/html/rfc4733.>. [cited by applicant]