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T1098.004 SSH Authorized Keys

Adversaries may modify the SSH authorized_keys file to maintain persistence on a victim host. Linux distributions and macOS commonly use key-based authentication to secure the authentication process of SSH sessions for remote management. The authorized_keys 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 <user-home>/.ssh/authorized_keys.6 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. The SSH config file is usually located under /etc/ssh/sshd_config.

Adversaries may modify SSH authorized_keys 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.42 Similarly, in Azure, an adversary may update the authorized_keys file of a virtual machine via a PATCH request to the API.5 This ensures that an adversary possessing the corresponding private key may log in as an existing user via SSH.13

Where authorized_keys files are modified via cloud APIs or command line interfaces, an adversary may achieve privilege escalation on the target virtual machine if they add a key to a higher-privileged user.

Item Value
ID T1098.004
Sub-techniques T1098.001, T1098.002, T1098.003, T1098.004, T1098.005
Tactics TA0003
Platforms IaaS, Linux, macOS
Version 1.1
Created 24 June 2020
Last Modified 20 April 2022

Procedure Examples

ID Name Description
S0482 Bundlore Bundlore creates a new key pair with ssh-keygen and drops the newly created user key in authorized_keys to enable remote login.8
S0468 Skidmap Skidmap has the ability to add the public key of its handlers to the authorized_keys file to maintain persistence on an infected host.7
G0139 TeamTNT TeamTNT has added RSA keys in authorized_keys.10
S0658 XCSSET XCSSET will create an ssh key if necessary with the ssh-keygen -t rsa -f $HOME/.ssh/id_rsa -P command. XCSSET will upload a private key file to the server to remotely access the host without a password.9


ID Mitigation Description
M1042 Disable or Remove Feature or Program Disable SSH if it is not necessary on a host or restrict SSH access for specific users/groups using /etc/ssh/sshd_config.
M1022 Restrict File and Directory Permissions Restrict access to the authorized_keys file.
M1018 User Account Management In cloud environments, ensure that only users who explicitly require the permissions to update instance metadata or configurations can do so.


ID Data Source Data Component
DS0017 Command Command Execution
DS0022 File File Modification
DS0009 Process Process Creation


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