Sub-technique of T1564 Hide Artifacts.View on attack.mitre.org
Adversaries may evade defensive mechanisms by executing commands that hide from process interrupt signals. Many operating systems use signals to deliver messages to control process behavior. Command interpreters often include specific commands/flags that ignore errors and other hangups, such as when the user of the active session logs off. These interrupt signals may also be used by defensive tools and/or analysts to pause or terminate specified running processes.
Adversaries may invoke processes using `nohup`, PowerShell `-ErrorAction SilentlyContinue`, or similar commands that may be immune to hangups. This may enable malicious commands and malware to continue execution through system events that would otherwise terminate its execution, such as users logging off or the termination of its C2 network connection.
Hiding from process interrupt signals may allow malware to continue execution, but unlike Trap this does not establish Persistence since the process will not be re-invoked once actually terminated.
Rules on DetectionCode tagged with T1564.011.
None recorded.
| Used by | Procedure example |
|---|---|
| GroupKimsuky | Kimsuky has leveraged the PowerShell `-ErrorAction SilentlyContinue` command to continue execution through system events. |
| GroupSea Turtle | Sea Turtle executed SnappyTCP using the tool NoHup, which keeps the malware running on a system after exiting the shell or terminal. |
| GroupUNC3886 | UNC3886 modified the startup file `/etc/init.d/localnet` to execute the line `nohup /bin/support &` so the script would run when the system was rebooted. |
| Used by | Procedure example |
|---|---|
| MalwareBOLDMOVE | BOLDMOVE calls the signal function to ignore the signals SIGCHLD, SIGHIP, and SIGPIPE prior to starting primary logic. |
| MalwareBPFDoor | BPFDoor sets its process to ignore the following signals; `SIGHUP`, `SIGINT`, `SIGQUIT`, `SIGPIPE`, `SIGCHLD`, `SIGTTIN`, and `SIGTTOU`. |
| MalwareGoldMax | The GoldMax Linux variant has been executed with the `nohup` command to ignore hangup signals and continue to run if the terminal session was terminated. |
| MalwareMini Shai-Hulud | Mini Shai-Hulud has suppressed output so that nothing is printed to terminal and has utilized silent exiting when environmental variables match restricted values. |
| MalwareOSX/Shlayer | OSX/Shlayer has used the `nohup` command to instruct executed payloads to ignore hangup signals. |
| MalwareShai-Hulud | Shai-Hulud has suppressed NPM warnings by silently exiting through the use of the NPM success code that has a setting that all errors exit with `code 0`. |
Data from MITRE ATT&CK® (Enterprise). ATT&CK® is a registered trademark of The MITRE Corporation.
