Potential Fileless Execution via Memory File Descriptor by LoLBin

[rule]
description = """
This rule detects when a process executes a file descriptor in the proc (temporary) file system via a LoLBin. 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 LoLBin, resulting in an exec event.
"""
id = "af4a2ea7-391f-4fc2-8ccf-946f412c023b"
license = "Elastic License v2"
name = "Potential Fileless Execution via Memory File Descriptor by LoLBin"
os_list = ["linux"]
reference = ["https://man7.org/linux/man-pages/man2/memfd_create.2.html"]
version = "1.0.3"

query = '''
process where event.type == "start" and event.action == "exec" and process.interactive == true and (
  process.name in (
    "bash", "dash", "sh", "tcsh", "tclsh", "wish", "csh", "zsh", "ksh", "fish", "mksh",
    "busybox", "pwsh", "node", "nodejs", "deno", "bun", "base64", "rscript", "escript",
    "r", "julia", "mono", "dotnet", "dotnet-ef", "groovy", "kotlin", "scala", "erlang",
    "ocaml", "ocamlopt", "ld.so", "ld-linux-x86-64.so.2", "awk", "gawk", "mawk", "nawk",
    "env", "timeout", "nice", "stdbuf", "setsid", "setarch", "unshare", "nsenter", "flock",
    "nohup", "runuser", "sudo", "snap", "snap-confine", "snap-exec", "erlexec", "beam.smp",
    "java", "javaw"
  ) or
  process.name like ("python*", "perl*", "ruby*", "lua*", "php*", "qemu-*-static")
) and
process.args regex """/proc/(self|[0-9]{1,7})/fd/[0-9]{1,7}""" and
not (
  process.command_line in ("ln -f -s /proc/1/fd/2 /docker.stderr", "ln -f -s /proc/1/fd/1 /docker.stdout") or
  process.parent.command_line like "*/home/*/.claude/shell-snapshots/snapshot-*" or
  process.parent.executable like (
    "/opt/omni/bin/drim/linux-amd64/coolie", "/bin/k3s", "/sbin/upstart", "/opt/hrt/hrtpylon-*/bin/python3.*",
    "/data/k3s/*/bin/k3s", "/var/lib/docker/overlay2/*/bin/k3s", "/var/lib/rancher/k3s/*/bin/k3s",
    "/usr/libexec/apptainer/bin/starter"
  ) or
  process.executable like "/home/*/core3/plz-out/bin/third_party/python3/cpython/usr/python3*/bin/python3.*" or
  (
    process.parent.executable == "/sbin/apk" and
    process.parent.args in ("add", "del", "upgrade")
  ) or
  (
    process.parent.executable == "/sbin/init" and
    process.name == "sh" and
    process.args == "-e"
  ) or
  (
    process.name == "busybox" and
    process.command_line == "tee -a /proc/1/fd/1"
  ) or
  (
    process.executable == "/bin/busybox" and
    process.args == "sh" and
    process.args in ("/usr/bin", "/usr/sbin")
  ) 
)
'''

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

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

[[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"