At.exe

Schedule periodic tasks

Paths

• C:\WINDOWS\System32\At.exe
• C:\WINDOWS\SysWOW64\At.exe

Commands

Execute

Create a recurring task to execute every day at a specific time.

Use case: Create a recurring task, to eg. to keep reverse shell session(s) alive

Privileges: Local Admin

C:\Windows\System32\at.exe 09:00 /interactive /every:m,t,w,th,f,s,su {CMD}

Detection

• Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/process_creation/proc_creation_win_at_interactive_execution.yml
• Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/network/zeek/zeek_smb_converted_win_atsvc_task.yml
• Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/builtin/security/win_security_atsvc_task.yml
• IOC: C:\Windows\System32\Tasks\At1 (substitute 1 with subsequent number of at job)
• IOC: C:\Windows\Tasks\At1.job
• IOC: Registry Key - Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree\At1.

Resources

• https://freddiebarrsmith.com/at.txt
• https://sushant747.gitbooks.io/total-oscp-guide/privilege_escalation_windows.html
• https://www.secureworks.com/blog/where-you-at-indicators-of-lateral-movement-using-at-exe-on-windows-7-systems