MITRE ATT&CK - Técnica

T1546.004: Unix Shell Configuration Modification

Unix Shell Configuration Modification (T1546.004) é uma técnica catalogada no MITRE ATT&CK Enterprise usada como referência para mapear comportamento adversário em auditorias de segurança.

Técnica T1546.004 Enterprise ATT&CK

Contexto para AppSec

Em uma auditoria de AppSec, Unix Shell Configuration Modification deve ser usada para revisar caminhos em que código, configuração, dependências ou infraestrutura podem viabilizar o comportamento descrito pela MITRE. No ATT&CK, ela aparece em Privilege Escalation e Persistence. As plataformas mapeadas pela MITRE incluem Linux e macOS. No Vigly, esse contexto ajuda a conectar evidências do repositório com priorização e remediação.

Tática/fase Privilege Escalation, Persistence
Plataformas MITRE Linux, macOS

Descrição oficial original do MITRE ATT&CK

Adversaries may establish persistence through executing malicious commands triggered by a user’s shell. User Unix Shells execute several configuration scripts at different points throughout the session based on events. For example, when a user opens a command-line interface or remotely logs in (such as via SSH) a login shell is initiated. The login shell executes scripts from the system (/etc) and the user’s home directory (/) to configure the environment. All login shells on a system use /etc/profile when initiated. These configuration scripts run at the permission level of their directory and are often used to set environment variables, create aliases, and customize the user’s environment. When the shell exits or terminates, additional shell scripts are executed to ensure the shell exits appropriately. Adversaries may attempt to establish persistence by inserting commands into scripts automatically executed by shells. Using bash as an example, the default shell for most GNU/Linux systems, adversaries may add commands that launch malicious binaries into the /etc/profile and /etc/profile.d files. These files typically require root permissions to modify and are executed each time any shell on a system launches. For user level permissions, adversaries can insert malicious commands into /.bash_profile, /.bash_login, or /.profile which are sourced when a user opens a command-line interface or connects remotely. Since the system only executes the first existing file in the listed order, adversaries have used /.bash_profile to ensure execution. Adversaries have also leveraged the /.bashrc file which is additionally executed if the connection is established remotely or an additional interactive shell is opened, such as a new tab in the command-line interface. Some malware targets the termination of a program to trigger execution, adversaries can use the /.bash_logout file to execute malicious commands at the end of a session. For macOS, the functionality of this technique is similar but may leverage zsh, the default shell for macOS 10.15+. When the Terminal.app is opened, the application launches a zsh login shell and a zsh interactive shell. The login shell configures the system environment using /etc/profile, /etc/zshenv, /etc/zprofile, and /etc/zlogin. The login shell then configures the user environment with /.zprofile and /.zlogin. The interactive shell uses the /.zshrc to configure the user environment. Upon exiting, /etc/zlogout and ~/.zlogout are executed. For legacy programs, macOS executes /etc/bashrc on startup.

Ver fonte oficial no MITRE ATT&CK

Como o Vigly audita a técnica Unix Shell Configuration Modification automaticamente na sua pipeline

O Vigly cruza sinais de SAST, modelagem de ameaças, regras de negócio e evidências do repositório para priorizar riscos reais antes que eles cheguem à produção.

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