Local Job Scheduling
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/Job 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.
Контрмеры |
|
| Контрмера | Описание |
|---|---|
| Local Job Scheduling Mitigation |
Limit privileges of user accounts and remediate Privilege Escalation vectors so only authorized users can create scheduled jobs. Identify and block unnecessary system utilities or potentially malicious software that may be used to schedule jobs using whitelisting tools. |
| User Account Management |
Manage the creation, modification, use, and permissions associated to user accounts. |
Обнаружение
Legitimate scheduled jobs may be created during installation of new software or through administration functions. Jobs scheduled with launchd and cron can be monitored from their respective utilities to list out detailed information about the jobs. Monitor process execution resulting from launchd and cron tasks to look for unusual or unknown applications and behavior.
Ссылки
- Threat Intelligence Team. (2015, January 6). Linux DDoS Trojan hiding itself with an embedded rootkit. Retrieved January 8, 2018.
- Patrick Wardle. (2015). Malware Persistence on OS X Yosemite. Retrieved July 10, 2017.
- Patrick Wardle. (2014, September). Methods of Malware Persistence on Mac OS X. Retrieved July 5, 2017.
- Thomas. (2013, July 15). New signed malware called Janicab. Retrieved July 17, 2017.
- Apple. (n.d.). Retrieved July 17, 2017.
- Thomas Koenig. (n.d.). at(1) - Linux man page. Retrieved December 19, 2017.
- Paul Vixie. (n.d.). crontab(5) - Linux man page. Retrieved December 19, 2017.
Связанные риски
Каталоги
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