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.[1] 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.[2][3] 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.
| ID | Name | Description |
|---|---|---|
| S1161 | BPFDoor |
BPFDoor set's it's process to ignore the following signals; |
| S0588 | GoldMax |
The GoldMax Linux variant has been executed with the |
| S0402 | OSX/Shlayer |
OSX/Shlayer has used the |
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
| ID | Data Source | Data Component | Detects |
|---|---|---|---|
| DS0017 | Command | Command Execution |
Monitor executed commands and arguments, such as |
| DS0009 | Process | Process Creation |
Monitor newly created processes for artifacts, such as |