Adversaries may register a device to an adversary-controlled account. Devices may be registered in a multifactor authentication (MFA) system, which handles authentication to the network, or in a device management system, which handles device access and compliance.

MFA systems, such as Duo or Okta, allow users to associate devices with their accounts in order to complete MFA requirements. An adversary that compromises a user’s credentials may enroll a new device in order to bypass initial MFA requirements and gain persistent access to a network.(Citation: CISA MFA PrintNightmare)(Citation: DarkReading FireEye SolarWinds) In some cases, the MFA self-enrollment process may require only a username and password to enroll the account's first device or to enroll a device to an inactive account. (Citation: Mandiant APT29 Microsoft 365 2022)

Similarly, an adversary with existing access to a network may register a device to Azure AD and/or its device management system, Microsoft Intune, in order to access sensitive data or resources while bypassing conditional access policies.(Citation: AADInternals - Device Registration)(Citation: AADInternals - Conditional Access Bypass)(Citation: Microsoft DEV-0537) 

Devices registered in Azure AD may be able to conduct [Internal Spearphishing](https://attack.mitre.org/techniques/T1534) campaigns via intra-organizational emails, which are less likely to be treated as suspicious by the email client.(Citation: Microsoft - Device Registration) Additionally, an adversary may be able to perform a [Service Exhaustion Flood](https://attack.mitre.org/techniques/T1499/002) on an Azure AD tenant by registering a large number of devices.(Citation: AADInternals - BPRT)
Device Registration
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1098/005  external_id: T1098.005     source_name: CISA MFA PrintNightmare  description: Cybersecurity and Infrastructure Security Agency. (2022, March 15). Russian State-Sponsored Cyber Actors Gain Network Access by Exploiting Default Multifactor Authentication Protocols and “PrintNightmare” Vulnerability. Retrieved March 16, 2022.  url: https://www.cisa.gov/uscert/ncas/alerts/aa22-074a     source_name: Mandiant APT29 Microsoft 365 2022  description: Douglas Bienstock. (2022, August 18). You Can’t Audit Me: APT29 Continues Targeting Microsoft 365. Retrieved February 23, 2023.  url: https://www.mandiant.com/resources/blog/apt29-continues-targeting-microsoft     source_name: AADInternals - Conditional Access Bypass  description: Dr. Nestori Syynimaa. (2020, September 6). Bypassing conditional access by faking device compliance. Retrieved March 4, 2022.  url: https://o365blog.com/post/mdm     source_name: AADInternals - BPRT  description: Dr. Nestori Syynimaa. (2021, January 31). BPRT unleashed: Joining multiple devices to Azure AD and Intune. Retrieved March 4, 2022.  url: https://o365blog.com/post/bprt/     source_name: AADInternals - Device Registration  description: Dr. Nestori Syynimaa. (2021, March 3). Deep-dive to Azure AD device join. Retrieved March 9, 2022.  url: https://o365blog.com/post/devices/     source_name: DarkReading FireEye SolarWinds  description: Kelly Jackson Higgins. (2021, January 7). FireEye's Mandia: 'Severity-Zero Alert' Led to Discovery of SolarWinds Attack. Retrieved April 18, 2022.  url: https://www.darkreading.com/threat-intelligence/fireeye-s-mandia-severity-zero-alert-led-to-discovery-of-solarwinds-attack     source_name: Microsoft - Device Registration  description: Microsoft 365 Defender Threat Intelligence Team. (2022, January 26). Evolved phishing: Device registration trick adds to phishers’ toolbox for victims without MFA. Retrieved March 4, 2022.  url: https://www.microsoft.com/security/blog/2022/01/26/evolved-phishing-device-registration-trick-adds-to-phishers-toolbox-for-victims-without-mfa     source_name: Microsoft DEV-0537  description: Microsoft. (2022, March 22). DEV-0537 criminal actor targeting organizations for data exfiltration and destruction. Retrieved March 23, 2022.  url: https://www.microsoft.com/security/blog/2022/03/22/dev-0537-criminal-actor-targeting-organizations-for-data-exfiltration-and-destruction/     