MASTG-BEST-0023 Exclude Sensitive Information from Backups (iOS)

• Platform: iOS
• Knowledge: MASTG-KNOW-0102

iOS does not provide a guaranteed mechanism to exclude files from backups. Setting NSURLIsExcludedFromBackupKey instructs the system not to include a file in backups, but it does not ensure exclusion. To reduce data exposure, apply the following techniques:

Bind Data to the Current Device

Store sensitive data in the Keychain and mark it with kSecAttrAccessibleWhenUnlockedThisDeviceOnly or kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly to keep secrets restricted to the current device. When implementing this, create a new Keychain entry and set the kSecAttrAccessible attribute to one of the ThisDeviceOnly values when inserting the item.

Handling Larger Files

For larger files, store them encrypted within the app container and keep the decryption key in the Keychain using a ThisDeviceOnly accessibility class. When you need to use the files, decrypt them only into RAM or into non‑backed‑up locations such as /Library/Caches or /tmp. Note that these locations are _purgeable_, and the system may delete their contents at any time; avoid treating them as durable storage. Be prepared to re‑decrypt the files on demand if they are cleared.

Bind Data to the User via a Server-Managed Key

If binding to the device is insufficient, you can instead bind data to a user by storing the decryption key on your server and releasing it only after successful authentication. Do not persist this key on the device; keep it only in RAM and decrypt files as described above.

1. Yleiskatsaus

1.1 Viittaukset

1.2 Tunnistetut vaatimukset

1.3 Liittyvät säädökset

2. Tunnistetut vaatimukset

3. Liittyvät säädökset

Linkitetyt tehtävät

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  • 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.
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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.