Query: mitigate SSH Authorized Keys
Matching passage: T1098.004 SSH Authorized Keys. Tactics: persistence, privilege escalation. Description: Adversaries may modify the SSH <code>authorized_keys</code> file to maintain persistence on a victim host. Linux distributions, macOS, and ESXi hypervisors commonly use key-based authentication to secure the authentication process of SSH sessions for remote management. The <code>authorized_keys</code> file in SSH specifies the SSH keys that can be used for logging into the user account for which the file is configured. This file is usually found in the user's home directory under <code>&lt;user-home&gt;/.ssh/authorized_keys</code> (or, on ESXi, `/etc/ssh/keys-<username>/authorized_keys`).(Citation: SSH Authorized Keys) Users may edit the system’s SSH config file to modify the directives `PubkeyAuthentication` and `RSAAuthentication` to the value `yes` to ensure public key and RSA authentication are enabled, as well as modify the directive `PermitRootLogin` to the value `yes` to enable root authentication via SSH.(Citation: Broadcom ESXi SSH) The SSH config file is usually located under <code>/etc/ssh/sshd_config</code>. Adversaries may modify SSH <code>authorized_keys</code> files directly with scripts or shell commands to add their own adversary-supplied public keys. In cloud environments, adversaries may be able to modify the SSH authorized_keys file of a particular virtual machine via the command line interface or rest API. For example, by using the Google Cloud CLI’s “add-metadata” command an adversary may add SSH keys to a user account.(Citation: Google Cloud Add Metadata)(Citation: Google Cloud Privilege Escalation) Similarly, in Azure, an adversary may update the authorized_keys file of a virtual machine via a PATCH request to the API.(Citation: Azure Update Virtual Machines) This ensures that an adversary possessing the corresponding private key may log in as an existing user via SSH.(Citation: Venafi SSH Key Abuse)(Citation: Cybereason Linux Exim Worm) It may also lead to privilege escalation where the virtual machine or instance has distinct permissions fr
Near-miss passage: T1098.005 Device Registration. Tactics: persistence, privilege escalation. Description: 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 or a virtual machine to Entra ID 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)(Citation: Expel Atlas Lion 2025) Devices registered in Entra ID 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 Entra ID tenant by registering a large number of devices.(Citation: AADInternals - BPRT)