T1546.005

Description from ATT&CK

Adversaries may establish persistence by executing malicious content triggered by an interrupt signal. The trap command allows programs and shells to specify commands that will be executed upon receiving interrupt signals. A common situation is a script allowing for graceful termination and handling of common keyboard interrupts like ctrl+c and ctrl+d.

Adversaries can use this to register code to be executed when the shell encounters specific interrupts as a persistence mechanism. Trap commands are of the following format trap 'command list' signals where "command list" will be executed when "signals" are received.(Citation: Trap Manual)(Citation: Cyberciti Trap Statements)

Source

Atomic Tests

• Atomic Test #1: Trap EXIT
• Atomic Test #2: Trap EXIT (freebsd)
• Atomic Test #3: Trap SIGINT
• Atomic Test #4: Trap SIGINT (freebsd)

Atomic Test #1: Trap EXIT

Launch bash shell with command arg to create TRAP on EXIT. The trap executes script that writes to /tmp/art-fish.txt

Supported Platforms: macOS, Linux

auto_generated_guid: a74b2e07-5952-4c03-8b56-56274b076b61

Attack Commands: Run with sh!

bash -c 'trap "nohup sh $PathToAtomicsFolder/T1546.005/src/echo-art-fish.sh" EXIT'

Cleanup Commands

rm -f /tmp/art-fish.txt

Atomic Test #2: Trap EXIT (freebsd)

Launch bash shell with command arg to create TRAP on EXIT. The trap executes script that writes to /tmp/art-fish.txt

Supported Platforms: Linux

auto_generated_guid: be1a5d70-6865-44aa-ab50-42244c9fd16f

Attack Commands: Run with sh!

bash -c 'trap "nohup sh $PathToAtomicsFolder/T1546.005/src/echo-art-fish.sh" EXIT'

Cleanup Commands

rm -f /tmp/art-fish.txt

Dependencies: Run with sh!

Description: Check if bash is installed.

Check Prereq Commands

if [ ! -x "$(command -v bash)" ]; then exit 1; else exit 0; fi;

Get Prereq Commands

(which pkg && pkg install -y bash)

Atomic Test #3: Trap SIGINT

Launch bash shell with command arg to create TRAP on SIGINT (CTRL+C), then send SIGINT signal. The trap executes script that writes to /tmp/art-fish.txt

Supported Platforms: macOS, Linux

auto_generated_guid: a547d1ba-1d7a-4cc5-a9cb-8d65e8809636

Attack Commands: Run with sh!

bash -c 'trap "nohup sh $PathToAtomicsFolder/T1546.005/src/echo-art-fish.sh" SIGINT && kill -SIGINT $$'

Cleanup Commands

rm -f /tmp/art-fish.txt

Atomic Test #4: Trap SIGINT (freebsd)

Launch bash shell with command arg to create TRAP on SIGINT (CTRL+C), then send SIGINT signal. The trap executes script that writes to /tmp/art-fish.txt

Supported Platforms: Linux

auto_generated_guid: ade10242-1eac-43df-8412-be0d4c704ada

Attack Commands: Run with sh!

bash -c 'trap "nohup sh $PathToAtomicsFolder/T1546.005/src/echo-art-fish.sh" SIGINT && kill -SIGINT $$'

Cleanup Commands

rm -f /tmp/art-fish.txt

Dependencies: Run with sh!

Description: Check if bash is installed.

Check Prereq Commands

if [ ! -x "$(command -v bash)" ]; then exit 1; else exit 0; fi;

Get Prereq Commands

(which pkg && pkg install -y bash)

Atomic test(s) for this technique last updated: 2023-11-06 22:41:43 UTC