+V6.6 Out-of-Band authentication mechanisms
---+V6.6.1 Verify that authentication mechanisms using the Public Switched Telephone Network (PSTN) to deliver …
---+V6.6.2 Verify that out-of-band authentication requests, codes, or tokens are bound to the original …
---+V6.6.3 Verify that a code based out-of-band authentication mechanism is protected against brute force …
---+V6.6.4 Verify that, where push notifications are used for multi-factor authentication, rate limiting is …

V6.6 Out-of-Band authentication mechanisms

This usually involves the authentication server communicating with a physical device over a secure secondary channel. For example, sending push notifications to mobile devices. This type of authentication mechanism is considered "something you have".

Unsafe out-of-band authentication mechanisms such as e-mail and VOIP are not permitted. PSTN and SMS authentication are currently considered to be "restricted" authentication mechanisms by NIST and should be deprecated in favor of Time based One-time Passwords (TOTPs), a cryptographic mechanism, or similar. NIST SP 800-63B § 5.1.3.3 recommends addressing the risks of device swap, SIM change, number porting, or other abnormal behavior, if telephone or SMS out-of-band authentication absolutely has to be supported. While this ASVS section does not mandate this as a requirement, not taking these precautions for a sensitive L2 app or an L3 app should be seen as a significant red flag.

Note that NIST has also recently provided guidance which discourages the use of push notifications. While this ASVS section does not do so, it is important to be aware of the risks of "push bombing".

1. Áttekintés

Megnevezés	Szabvány
V6.6.1 Verify that authentication mechanisms using the Public Switched Telephone Network (PSTN) to deliver …	Verify that authentication mechanisms using the Public Switched Telephone Network (PSTN) to deliver One-time Passwords (OTPs) via phone or SMS are offered only when the phone number has previously been validated, alternate stronger methods (such as Time based One-time Passwords) are also offered, and the service provides information on their security risks to users. For L3 applications, phone and SMS must not be available as options.
V6.6.2 Verify that out-of-band authentication requests, codes, or tokens are bound to the original …	Verify that out-of-band authentication requests, codes, or tokens are bound to the original authentication request for which they were generated and are not usable for a previous or subsequent one.
V6.6.3 Verify that a code based out-of-band authentication mechanism is protected against brute force …	Verify that a code based out-of-band authentication mechanism is protected against brute force attacks by using rate limiting. Consider also using a code with at least 64 bits of entropy.
V6.6.4 Verify that, where push notifications are used for multi-factor authentication, rate limiting is …	Verify that, where push notifications are used for multi-factor authentication, rate limiting is used to prevent push bombing attacks. Number matching may also mitigate this risk.

1.1 Hivatkozások

1.2 Azonosított követelmények

1.3 Kapcsolódó szabályozások

2. Azonosított követelmények

Követelmények
Forrás	Követelmény

3. Kapcsolódó szabályozások

Szabályozások
Forrás	Szabályozás

OWASP -
EN: Publications of the OWASP Foundation, https://owasp.org/. OWASP® is a registered trademark of the OWASP Foundation, Inc.; GRCA is not affiliated with, nor endorsed by, the OWASP Foundation. Only the versions published by OWASP are authoritative.
- OWASP Application Security Verification Standard (ASVS) 5.0.0, May 2025, from OWASP/ASVS: © 2008-2025 The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: divided into sections and converted into the GRCA format, the wording unchanged. These adaptations are shared under CC BY-SA 4.0 as well.
- OWASP Mobile Application Security Verification Standard (MASVS) v2.1.0, January 2024, from OWASP/masvs: © The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: converted into the GRCA format, the wording unchanged. These adaptations are shared under CC BY-SA 4.0 as well.
- OWASP Mobile Application Security Weakness Enumeration (MASWE) v1.0.0, August 2026, from OWASP/maswe: © The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: converted into the GRCA format, the wording unchanged, linked to the MASVS controls they map to. These adaptations are shared under CC BY-SA 4.0 as well.
- OWASP Mobile Application Security Testing Guide (MASTG) v2.0.0, June 2026, from OWASP/mastg: © The OWASP Foundation, licensed under CC BY-SA 4.0. The tests and best practices only, without code samples, images, tools or apps. Changes: converted into the GRCA format, the wording unchanged; references to other pages of the MASTG as links to mas.owasp.org; the weakness of each test in the numbering of MASWE v1 and linked to it. These adaptations are shared under CC BY-SA 4.0 as well.
- OWASP Software Assurance Maturity Model (SAMM) v2.2.0, July 2026, from owaspsamm/core: © The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: converted into the GRCA format, the wording unchanged; short codes (G-SM-1-A) built from the model, the assessment questions as assessment procedures of their activities. These adaptations are shared under CC BY-SA 4.0 as well.
- OWASP Top 10:2025, from OWASP/Top10: © 2003-2025 The OWASP® Foundation, Inc., licensed under CC BY-SA 4.0. The ten categories, without the icons. Changes: converted into the GRCA format, the wording unchanged. These adaptations are shared under CC BY-SA 4.0 as well. The names of the mapped CWEs (Common Weakness Enumeration): © 2006–2026 The MITRE Corporation. License: The MITRE Corporation hereby grants you a non-exclusive, royalty-free license to use CWE for research, development, and commercial purposes. Any copy you make for such purposes is authorized on the condition that you reproduce MITRE’s copyright designation and this license in any such copy. See the CWE Terms of Use. CWE™ is a trademark of The MITRE Corporation.
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- OWASP Application Security Verification Standard (ASVS) 5.0.0, Mai 2025, aus OWASP/ASVS: © 2008-2025 The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in Abschnitte aufgeteilt und in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
- OWASP Mobile Application Security Verification Standard (MASVS) v2.1.0, Januar 2024, aus OWASP/masvs: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
- OWASP Mobile Application Security Weakness Enumeration (MASWE) v1.0.0, August 2026, aus OWASP/maswe: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert, mit den MASVS-Controls verknüpft, denen sie zugeordnet sind. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
- OWASP Mobile Application Security Testing Guide (MASTG) v2.0.0, Juni 2026, aus OWASP/mastg: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Nur die Tests und Best Practices, ohne Codebeispiele, Bilder, Werkzeuge und Apps. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Verweise auf andere Seiten des MASTG als Links zu mas.owasp.org; die Schwachstelle jedes Tests in der Nummerierung der MASWE v1 und mit ihr verknüpft. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
- OWASP Software Assurance Maturity Model (SAMM) v2.2.0, Juli 2026, aus owaspsamm/core: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Kürzel (G-SM-1-A) aus dem Modell gebildet, die Assessment-Fragen als Prüfverfahren ihrer Aktivitäten. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
- OWASP Top 10:2025, aus OWASP/Top10: © 2003-2025 The OWASP® Foundation, Inc., lizenziert unter CC BY-SA 4.0. Die zehn Kategorien, ohne die Symbole. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0. Die Namen der zugeordneten CWEs (Common Weakness Enumeration): © 2006–2026 The MITRE Corporation. MITRE erlaubt die Nutzung für Forschung, Entwicklung und kommerzielle Zwecke, wenn jede Kopie den Urheberrechtsvermerk und die Lizenz enthält; maßgeblich ist der englische Wortlaut der Lizenz oben und die CWE Terms of Use. CWE™ ist eine Marke der MITRE Corporation.