Scheduled Task/Job: Утилита at
Other sub-techniques of Scheduled Task/Job (7)
Adversaries may abuse the at utility to perform task scheduling for initial or recurring execution of malicious code. The at utility exists as an executable within Windows, Linux, and macOS for scheduling tasks at a specified time and date. Although deprecated in favor of Scheduled Task's schtasks in Windows environments, using at requires that the Task Scheduler service be running, and the user to be logged on as a member of the local Administrators group.
On Linux and macOS, at may be invoked by the superuser as well as any users added to the at.allow file. If the at.allow file does not exist, the at.deny file is checked. Every username not listed in at.deny is allowed to invoke at. If the at.deny exists and is empty, global use of at is permitted. If neither file exists (which is often the baseline) only the superuser is allowed to use at.(Citation: Linux at)
Adversaries may use at to execute programs at system startup or on a scheduled basis for Persistence. at can also be abused to conduct remote Execution as part of Lateral Movement and/or to run a process under the context of a specified account (such as SYSTEM).
In Linux environments, adversaries may also abuse at to break out of restricted environments by using a task to spawn an interactive system shell or to run system commands. Similarly, at may also be used for Privilege Escalation if the binary is allowed to run as superuser via sudo.(Citation: GTFObins at)
Примеры процедур |
|
| Название | Описание |
|---|---|
| Threat Group-3390 |
Threat Group-3390 actors use at to schedule tasks to run self-extracting RAR archives, which install HTTPBrowser or PlugX on other victims on a network.(Citation: Dell TG-3390) |
| CrackMapExec |
CrackMapExec can set a scheduled task on the target system to execute commands remotely using at.(Citation: CME Github September 2018) |
| APT18 |
APT18 actors used the native at Windows task scheduler tool to use scheduled tasks for execution on a victim network.(Citation: Dell Lateral Movement) |
| BRONZE BUTLER |
BRONZE BUTLER has used at to register a scheduled task to execute malware during lateral movement.(Citation: Secureworks BRONZE BUTLER Oct 2017) |
| MURKYTOP |
MURKYTOP has the capability to schedule remote AT jobs.(Citation: FireEye Periscope March 2018) |
| at |
at can be used to schedule a task on a system to be executed at a specific date or time.(Citation: TechNet At)(Citation: Linux at) |
Контрмеры |
|
| Контрмера | Описание |
|---|---|
| Operating System Configuration |
Make configuration changes related to the operating system or a common feature of the operating system that result in system hardening against techniques. |
| Audit |
Perform audits or scans of systems, permissions, insecure software, insecure configurations, etc. to identify potential weaknesses. |
| User Account Management |
Manage the creation, modification, use, and permissions associated to user accounts. |
| Privileged Account Management |
Manage the creation, modification, use, and permissions associated to privileged accounts, including SYSTEM and root. |
Обнаружение
Monitor process execution from the svchost.exe in Windows 10 and the Windows Task Scheduler taskeng.exe for older versions of Windows. (Citation: Twitter Leoloobeek Scheduled Task) If scheduled tasks are not used for persistence, then the adversary is likely to remove the task when the action is complete. Monitor Windows Task Scheduler stores in %systemroot%\System32\Tasks for change entries related to scheduled tasks that do not correlate with known software, patch cycles, etc.
Configure event logging for scheduled task creation and changes by enabling the "Microsoft-Windows-TaskScheduler/Operational" setting within the event logging service. (Citation: TechNet Forum Scheduled Task Operational Setting) Several events will then be logged on scheduled task activity, including: (Citation: TechNet Scheduled Task Events)(Citation: Microsoft Scheduled Task Events Win10)
* Event ID 106 on Windows 7, Server 2008 R2 - Scheduled task registered
* Event ID 140 on Windows 7, Server 2008 R2 / 4702 on Windows 10, Server 2016 - Scheduled task updated
* Event ID 141 on Windows 7, Server 2008 R2 / 4699 on Windows 10, Server 2016 - Scheduled task deleted
* Event ID 4698 on Windows 10, Server 2016 - Scheduled task created
* Event ID 4700 on Windows 10, Server 2016 - Scheduled task enabled
* Event ID 4701 on Windows 10, Server 2016 - Scheduled task disabled
Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including listing current scheduled tasks. (Citation: TechNet Autoruns)
Remote access tools with built-in features may interact directly with the Windows API to perform these functions outside of typical system utilities. Tasks may also be created through Windows system management tools such as Windows Management Instrumentation and PowerShell, so additional logging may need to be configured to gather the appropriate data.
In Linux and macOS environments, monitor scheduled task creation using command-line invocation. Legitimate scheduled tasks may be created during installation of new software or through system administration functions. Look for changes to tasks that do not correlate with known software, patch cycles, etc.
Review all jobs using the atq command and ensure IP addresses stored in the SSH_CONNECTION and SSH_CLIENT variables, machines that created the jobs, are trusted hosts. All at jobs are stored in /var/spool/cron/atjobs/.(Citation: rowland linux at 2019)
Suspicious program execution through scheduled tasks may show up as outlier processes that have not been seen before when compared against historical data. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.
Ссылки
- Satyajit321. (2015, November 3). Scheduled Tasks History Retention settings. Retrieved December 12, 2017.
- Russinovich, M. (2016, January 4). Autoruns for Windows v13.51. Retrieved June 6, 2016.
- Microsoft. (n.d.). General Task Registration. Retrieved December 12, 2017.
- Microsoft. (2017, May 28). Audit Other Object Access Events. Retrieved June 27, 2019.
- Loobeek, L. (2017, December 8). leoloobeek Status. Retrieved December 12, 2017.
- IEEE/The Open Group. (2017). at(1p) — Linux manual page. Retrieved February 25, 2022.
- Emilio Pinna, Andrea Cardaci. (n.d.). gtfobins at. Retrieved September 28, 2021.
- Craig Rowland. (2019, July 25). Getting an Attacker IP Address from a Malicious Linux At Job. Retrieved October 15, 2021.
- Microsoft. (2013, May 8). Increase scheduling priority. Retrieved December 18, 2017.
- FireEye. (2018, March 16). Suspected Chinese Cyber Espionage Group (TEMP.Periscope) Targeting U.S. Engineering and Maritime Industries. Retrieved April 11, 2018.
- Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, August 5). Threat Group-3390 Targets Organizations for Cyberespionage. Retrieved August 18, 2018.
- PowerSploit. (n.d.). Retrieved December 4, 2014.
- Koromicha. (2019, September 7). Scheduling tasks using at command in Linux. Retrieved December 3, 2019.
- Carvey, H.. (2014, September). Where You AT?: Indicators of Lateral Movement Using at.exe on Windows 7 Systems. Retrieved November 27, 2019.
- byt3bl33d3r. (2018, September 8). SMB: Command Reference. Retrieved July 17, 2020.
- Carvey, H.. (2014, September 2). Where you AT?: Indicators of lateral movement using at.exe on Windows 7 systems. Retrieved January 25, 2016.
- Counter Threat Unit Research Team. (2017, October 12). BRONZE BUTLER Targets Japanese Enterprises. Retrieved January 4, 2018.
- Microsoft. (n.d.). At. Retrieved April 28, 2016.
- Microsoft. (2012, November 15). Domain controller: Allow server operators to schedule tasks. Retrieved December 18, 2017.
Связанные риски
| Риск | Связи | |
|---|---|---|
|
Закрепление злоумышленника в ОС из-за
создания или изменение задачи утилитой AT в ОС Linux
Повышение привилегий
НСД
|
1
|
|
|
Повышение привилегий в ОС из-за
создания или изменение задачи утилитой AT в ОС Linux
Повышение привилегий
Целостность
|
1
|
|
|
Заражение вредоносным программным обеспечением из-за
создания или изменение задачи утилитой AT в ОС Linux
Доступность
Конфиденциальность
Отказ в обслуживании
Повышение привилегий
Раскрытие информации
Целостность
Искажение
|
1
|
|
|
Повышение привилегий в ОС из-за
создания или изменение задачи утилитой AT в ОС Windows
Повышение привилегий
Целостность
|
|
|
|
Заражение вредоносным программным обеспечением из-за
создания или изменение задачи утилитой AT в ОС Windows
Доступность
Конфиденциальность
Отказ в обслуживании
Повышение привилегий
Раскрытие информации
Целостность
Искажение
|
1
|
|
|
Закрепление злоумышленника в ОС из-за
создания или изменение задачи утилитой AT в ОС Windows
Повышение привилегий
НСД
|
|
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