legitimate user shell modification activity.

Techniques

T1546

Sample rules

Shell Configuration Creation or Modification

source: elastic
technicques:
- T1546

Description

This rule monitors the creation/alteration of a shell configuration file. Unix systems use shell configuration files to set environment variables, create aliases, and customize the user’s environment. Adversaries may modify or add a shell configuration file to execute malicious code and gain persistence in the system. This behavior is consistent with the Kaiji malware family.

Detection logic

file where host.os.type == "linux" and event.action in ("rename", "creation") and file.path : (
  // system-wide configurations
  "/etc/profile", "/etc/profile.d/*", "/etc/bash.bashrc", "/etc/bash.bash_logout", "/etc/zsh/*",
  "/etc/csh.cshrc", "/etc/csh.login", "/etc/fish/config.fish", "/etc/ksh.kshrc",
  // root and user configurations
  "/home/*/.profile", "/home/*/.bashrc", "/home/*/.bash_login", "/home/*/.bash_logout", "/home/*/.bash_profile",
  "/root/.profile", "/root/.bashrc", "/root/.bash_login", "/root/.bash_logout", "/root/.bash_profile",
  "/home/*/.zprofile", "/home/*/.zshrc", "/root/.zprofile", "/root/.zshrc",
  "/home/*/.cshrc", "/home/*/.login", "/home/*/.logout", "/root/.cshrc", "/root/.login", "/root/.logout",
  "/home/*/.config/fish/config.fish", "/root/.config/fish/config.fish",
  "/home/*/.kshrc", "/root/.kshrc"
) and not (
  process.executable in (
    "/bin/dpkg", "/usr/bin/dpkg", "/bin/dockerd", "/usr/bin/dockerd", "/usr/sbin/dockerd", "/bin/microdnf",
    "/usr/bin/microdnf", "/bin/rpm", "/usr/bin/rpm", "/bin/snapd", "/usr/bin/snapd", "/bin/yum", "/usr/bin/yum",
    "/bin/dnf", "/usr/bin/dnf", "/bin/podman", "/usr/bin/podman", "/bin/dnf-automatic", "/usr/bin/dnf-automatic",
    "/bin/pacman", "/usr/bin/pacman", "/usr/bin/dpkg-divert", "/bin/dpkg-divert", "/sbin/apk", "/usr/sbin/apk",
    "/usr/local/sbin/apk", "/usr/bin/apt", "/usr/sbin/pacman", "/bin/podman", "/usr/bin/podman", "/usr/bin/puppet",
    "/bin/puppet", "/opt/puppetlabs/puppet/bin/puppet", "/usr/bin/chef-client", "/bin/chef-client",
    "/bin/autossl_check", "/usr/bin/autossl_check", "/proc/self/exe", "/dev/fd/*",  "/usr/bin/pamac-daemon",
    "/bin/pamac-daemon", "/usr/lib/snapd/snapd", "/usr/sbin/adduser", "/usr/sbin/useradd", "/usr/local/bin/dockerd",
    "/usr/sbin/gdm", "/usr/bin/unzip", "/usr/bin/gnome-shell", "/sbin/mkhomedir_helper", "/usr/sbin/sshd",
    "/opt/puppetlabs/puppet/bin/ruby", "/usr/bin/xfce4-session", "/usr/libexec/oddjob/mkhomedir", "/sbin/useradd",
    "/usr/lib/systemd/systemd", "/usr/sbin/crond", "/usr/bin/pamac-daemon", "/usr/sbin/mkhomedir_helper",
    "/opt/pbis/sbin/lwsmd", "/usr/sbin/oddjobd"
  ) or
  file.extension in ("swp", "swpx", "swx", "dpkg-remove") or
  file.Ext.original.extension == "dpkg-new" or
  process.executable : (
    "/nix/store/*", "/var/lib/dpkg/*", "/tmp/vmis.*", "/snap/*", "/dev/fd/*", "/usr/lib/virtualbox/*",
    "/usr/libexec/platform-python*"
  ) or
  process.executable == null or
  process.name in ("adclient", "mkhomedir_helper", "teleport", "mkhomedir", "adduser", "desktopDaemon") or
  (process.name == "sed" and file.name : "sed*") or
  (process.name == "perl" and file.name : "e2scrub_all.tmp*") 
)