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T1168 - Local Job Scheduling

Description from ATT&CK

On Linux and macOS systems, multiple methods are supported for creating pre-scheduled and periodic background jobs: cron, (Citation: Die.net Linux crontab Man Page) at, (Citation: Die.net Linux at Man Page) and launchd. (Citation: AppleDocs Scheduling Timed Jobs) Unlike [Scheduled Task](https://attack.mitre.org/techniques/T1053) on Windows systems, job scheduling on Linux-based systems cannot be done remotely unless used in conjunction within an established remote session, like secure shell (SSH).

cron

System-wide cron jobs are installed by modifying /etc/crontab file, /etc/cron.d/ directory or other locations supported by the Cron daemon, while per-user cron jobs are installed using crontab with specifically formatted crontab files. (Citation: AppleDocs Scheduling Timed Jobs) This works on macOS and Linux systems.

Those methods allow for commands or scripts to be executed at specific, periodic intervals in the background without user interaction. An adversary may use job scheduling to execute programs at system startup or on a scheduled basis for Persistence, (Citation: Janicab) (Citation: Methods of Mac Malware Persistence) (Citation: Malware Persistence on OS X) (Citation: Avast Linux Trojan Cron Persistence) to conduct Execution as part of Lateral Movement, to gain root privileges, or to run a process under the context of a specific account.

at

The at program is another means on POSIX-based systems, including macOS and Linux, to schedule a program or script job for execution at a later date and/or time, which could also be used for the same purposes.

launchd

Each launchd job is described by a different configuration property list (plist) file similar to Launch Daemon or Launch Agent, except there is an additional key called StartCalendarInterval with a dictionary of time values. (Citation: AppleDocs Scheduling Timed Jobs) This only works on macOS and OS X.

Atomic Tests


Atomic Test #1 - Cron - Replace crontab with referenced file

This test replaces the current user's crontab file with the contents of the referenced file. This technique was used by numerous IoT automated exploitation attacks.

Supported Platforms: macOS, CentOS, Ubuntu, Linux

Inputs

Name Description Type Default Value
command Command to execute string /tmp/evil.sh
tmp_cron Temporary reference file to hold evil cron schedule path /tmp/persistevil

Run it with bash!

echo "* * * * * #{command}" > #{tmp_cron} && crontab #{tmp_cron}


Atomic Test #2 - Cron - Add script to cron folder

This test adds a script to a cron folder configured to execute on a schedule. This technique was used by the threat actor Rocke during the exploitation of Linux web servers.

Supported Platforms: macOS, CentOS, Ubuntu, Linux

Inputs

Name Description Type Default Value
command Command to execute string echo 'Hello from Atomic Red Team' > /tmp/atomic.log
cron_script_name Name of file to store in cron folder string persistevil

Run it with bash!

echo "#{command}" > /etc/cron.daily/#{cron_script_name}


Atomic Test #3 - Event Monitor Daemon Persistence

This test adds persistence via a plist to execute via the macOS Event Monitor Daemon.

Supported Platforms: macOS, CentOS, Ubuntu, Linux

Run it with these steps!

  1. Place this file in /etc/emond.d/rules/atomicredteam.plist
name atomicredteam enabled eventTypes startup actions command /usr/bin/say user root arguments -v Tessa I am a persistent startup item. type RunCommand

  1. Place an empty file in /private/var/db/emondClients/

  2. sudo touch /private/var/db/emondClients/randomflag