T1053.006
Scheduled Task/Job: Systemd Timers
Description from ATT&CK
Adversaries may abuse systemd timers to perform task scheduling for initial or recurring execution of malicious code. Systemd timers are unit files with file extension .timer that control services. Timers can be set to run on a calendar event or after a time span relative to a starting point. They can be used as an alternative to Cron in Linux environments.(Citation: archlinux Systemd Timers Aug 2020) Systemd timers may be activated remotely via the systemctl command line utility, which operates over SSH.(Citation: Systemd Remote Control)
Each .timer file must have a corresponding .service file with the same name, e.g., example.timer and example.service. .service files are Systemd Service unit files that are managed by the systemd system and service manager.(Citation: Linux man-pages: systemd January 2014) Privileged timers are written to /etc/systemd/system/ and /usr/lib/systemd/system while user level are written to ~/.config/systemd/user/.
An adversary may use systemd timers to execute malicious code at system startup or on a scheduled basis for persistence.(Citation: Arch Linux Package Systemd Compromise BleepingComputer 10JUL2018)(Citation: gist Arch package compromise 10JUL2018)(Citation: acroread package compromised Arch Linux Mail 8JUL2018) Timers installed using privileged paths may be used to maintain root level persistence. Adversaries may also install user level timers to achieve user level persistence.(Citation: Falcon Sandbox smp: 28553b3a9d)
Atomic Tests
Atomic Test #1 - Create Systemd Service and Timer
This test creates Systemd service and timer then starts and enables the Systemd timer
Supported Platforms: linux
auto_generated_guid: f4983098-bb13-44fb-9b2c-46149961807b
Inputs:
| Name | Description | Type | Default Value |
|---|---|---|---|
| path_to_systemd_service | Path to systemd service unit file | path | /etc/systemd/system/art-timer.service |
| path_to_systemd_timer | Path to service timer file | path | /etc/systemd/system/art-timer.timer |
| systemd_service_name | Name of systemd service | string | art-timer.service |
| systemd_timer_name | Name of systemd service timer | string | art-timer.timer |
Attack Commands: Run with bash!
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echo "[Unit]" > #{path_to_systemd_service}
echo "Description=Atomic Red Team Systemd Timer Service" >> #{path_to_systemd_service}
echo "[Service]" >> #{path_to_systemd_service}
echo "Type=simple" >> #{path_to_systemd_service}
echo "ExecStart=/bin/touch /tmp/art-systemd-timer-marker" >> #{path_to_systemd_service}
echo "[Install]" >> #{path_to_systemd_service}
echo "WantedBy=multi-user.target" >> #{path_to_systemd_service}
echo "[Unit]" > #{path_to_systemd_timer}
echo "Description=Executes Atomic Red Team Systemd Timer Service" >> #{path_to_systemd_timer}
echo "Requires=#{systemd_service_name}" >> #{path_to_systemd_timer}
echo "[Timer]" >> #{path_to_systemd_timer}
echo "Unit=#{systemd_service_name}" >> #{path_to_systemd_timer}
echo "OnCalendar=*-*-* *:*:00" >> #{path_to_systemd_timer}
echo "[Install]" >> #{path_to_systemd_timer}
echo "WantedBy=timers.target" >> #{path_to_systemd_timer}
systemctl start #{systemd_timer_name}
systemctl enable #{systemd_timer_name}
systemctl daemon-reload
Cleanup Commands:
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systemctl stop #{systemd_timer_name}
systemctl disable #{systemd_timer_name}
rm #{path_to_systemd_service}
rm #{path_to_systemd_timer}
systemctl daemon-reload
Atomic Test #2 - Create a user level transient systemd service and timer
Schedule a user level transient task (will not survive a reboot) without having to create the .timer or .service files by using the systemd-run command.
Supported Platforms: linux
auto_generated_guid: 3de33f5b-62e5-4e63-a2a0-6fd8808c80ec
Inputs:
None
Attack Commands: Run with sh!
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systemd-run --user --unit=Atomic-Red-Team --on-calendar '*:0/1' /bin/sh -c 'echo "$(date) $(whoami)" >>/tmp/log'
Cleanup Commands:
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systemctl --user stop Atomic-Red-Team.service
systemctl --user stop Atomic-Red-Team.timer
rm /tmp/log
Dependencies: Run with sh!
Description: Check if systemd-run exists on the machine
Check Prereq Commands:
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if [ -x "$(command -v systemd-run)" ]; then exit 0; else exit 1; fi;
Get Prereq Commands:
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echo "Install systemd on the machine."; exit 1;
Atomic Test #3 - Create a system level transient systemd service and timer
Schedule a system level transient task (will not survive a reboot) without having to create the .timer or .service files by using the systemd-run command.
Supported Platforms: linux
auto_generated_guid: d3eda496-1fc0-49e9-aff5-3bec5da9fa22
Inputs:
None
Attack Commands: Run with sh! Elevation Required (e.g. root or admin)
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systemd-run --unit=Atomic-Red-Team --on-calendar '*:0/1' /bin/sh -c 'echo "$(date) $(whoami)" >>/tmp/log'
Cleanup Commands:
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systemctl stop Atomic-Red-Team.service
systemctl stop Atomic-Red-Team.timer
rm /tmp/log
Dependencies: Run with sh!
Description: Check if systemd-run exists on the machine
Check Prereq Commands:
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if [ -x "$(command -v systemd-run)" ]; then exit 0; else exit 1; fi;
Get Prereq Commands:
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echo "Install systemd on the machine."; exit 1;