Potential Fileless Execution Sequence

[rule]
description = """
This rule detects when a process creates an in-memory file using the memfd_create syscall followed by executing a file
descriptor in the proc (temporary) file system. This activity indicates an active attempt to execute a fileless payload
and should be considered highly abnormal or suspicious. This activity can occur when the memfd syscall is utilized to
create a memory resident file, like a payload, and then uses it to execute a process via a command and control channel
via a file descriptor in the proc (temporary) file system, resulting in an exec event.
"""
id = "03e8852f-d736-42ec-ae61-9e3fb1847d83"
license = "Elastic License v2"
name = "Potential Fileless Execution Sequence"
os_list = ["linux"]
reference = ["https://man7.org/linux/man-pages/man2/memfd_create.2.html"]
version = "1.0.3"

query = '''
sequence by process.entity_id with maxspan=5s
  [process where event.type == "start" and event.action == "memfd_create" and
  not (
    (
      process.executable like ("/usr/sbin/runc", "/snap/microk8s/*/bin/runc") and
      process.Ext.memfd.name == "memfd:runc_cloned:/proc/self/exe"
    ) or
    (
     process.executable like "/nix/store/*/bin/buildah" and
     process.Ext.memfd.name == "memfd:buildah-in-a-user-namespace"
    ) or
    process.executable like ("/usr/bin/lxc-attach", "memfd:buildah-chroot-runtime", "./usr/bin/nvidia-cdi-hook") or
    process.command_line == "buildah-chroot-runtime"
  )]
  [process where event.type == "start" and event.action == "exec" and (
    process.args regex """/proc/(self|[0-9]{1,7})/fd/[0-9]{1,7}""" or
    process.executable like ("memfd:*", "?memfd:*")
  ) and
  not process.executable in ("memfd:runc_cloned:/proc/self/exe", "/usr/bin/nvidia-ctk")]
'''

min_endpoint_version = "9.1.4"
optional_actions = []
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0

[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 1

[[actions]]
action = "kill_process"
field = "process.parent.entity_id"
state = 0

[[actions]]
action = "kill_process"
field = "process.parent.entity_id"
state = 1

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1106"
name = "Native API"
reference = "https://attack.mitre.org/techniques/T1106/"


[threat.tactic]
id = "TA0002"
name = "Execution"
reference = "https://attack.mitre.org/tactics/TA0002/"
[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1055"
name = "Process Injection"
reference = "https://attack.mitre.org/techniques/T1055/"
[[threat.technique.subtechnique]]
id = "T1055.009"
name = "Proc Memory"
reference = "https://attack.mitre.org/techniques/T1055/009/"


[[threat.technique]]
id = "T1620"
name = "Reflective Code Loading"
reference = "https://attack.mitre.org/techniques/T1620/"


[threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"

[internal]
min_endpoint_version = "9.1.4"