PhoneFactor explained

PhoneFactor is a proprietary multi-factor authentication owned by Microsoft. It uses telephone calls, SMS messages, and push notifications to verify identity.^{[1] [2]}

PhoneFactor was originally developed by Positive Networks Inc., founded in 2001 by Tim Sutton and Steve Dispensa. The PhoneFactor product was launched in 2007,^[3] and the company changed their name to PhoneFactor Inc. in 2009.^{[4] [5]} On October 4, 2012, Microsoft acquired PhoneFactor,^[6] and the PhoneFactor service is now available as Azure Multi-Factor Authentication. In addition to securing on-premises applications and identities, the service now also works with cloud applications like Microsoft 365 that use Windows Microsoft Azure Active Directory.

Notes and References

1. Haiyang Qian . Chandra S. Surapaneni . Steve Dispensa . Deep Medhi . IFIP/IEEE International Symposium on Integrated Network Management (IM'2009) . June 2009 . Service Management Architecture and System Capacity Design for PhoneFactor--A Two-Factor Authentication Service . dead . https://web.archive.org/web/20130927160703/http://sce.umkc.edu/~dmedhi/papers/qsdm-im09.pdf . 2013-09-27 .
2. Haiyang Qian . Chandra S. Surapaneni . Marsh Ray . Steve Dispensa . Deep Medhi . DReaM-Cache: Distributed Real-Time Transaction Memory Cache to Support Two-Factor Authentication Services and its Reliability . IEEE/IFIP Network Operations and Management Symposium (NOMS'2010) . April 2010 . dead . https://web.archive.org/web/20130927160922/http://sce.umkc.edu/~dmedhi/papers/qsrdm-noms2010.pdf . 2013-09-27 .
3. Two-Factor Authentication Without Tokens: Positive Networks Debuts PhoneFactor(TM) . 11 July 2018 . Business Wire . 22 May 2007 . en.
4. News: Positive Networks changes name to PhoneFactor. Kansas City Business Journal . bizjournals.com . 11 July 2018 . 7 January 2009.
5. News: Quain. John R.. Logging on Securely, and Confirmed via a Cellphone Call as a Sentinel Against Intruders. New York Times / NYT.com. 8 Oct 2008.
6. News: Microsoft buys security vendor PhoneFactor. Computerworld. 4 Oct 2012.