Network Activity via (Memory) File Descriptor

[rule]
description = """
This rule detects when a process creates a (memory) file descriptor and attempts, or accepts, a network connection. 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 used to create a memory-resident file, such as a payload,
and then execute it, after which it establishes outbound network connections for command-and-control (C2).
"""
id = "0e87bfb7-42e5-4543-8e97-713fdbca0f4b"
license = "Elastic License v2"
name = "Network Activity via (Memory) File Descriptor"
os_list = ["linux"]
reference = ["https://man7.org/linux/man-pages/man2/memfd_create.2.html"]
version = "1.0.3"

query = '''
network where event.type == "start" and (
  process.executable regex """/proc/(self|[0-9]{1,7})/fd/[0-9]{1,7}""" or
  process.executable like ("memfd:*", "?memfd:*")
) and
not (
  destination.ip == null or
  destination.ip == "0.0.0.0" or
  cidrmatch(
    destination.ip, "10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.0.0.0/24", "192.0.0.0/29",
    "192.0.0.8/32", "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24",
    "192.31.196.0/24", "192.52.193.0/24", "192.168.0.0/16", "192.88.99.0/24", "224.0.0.0/4", "100.64.0.0/10",
    "192.175.48.0/24","198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1", "FE80::/10",
    "FF00::/8"
  ) or
  (process.executable == "/memfd: (deleted)" and user.name == "nordlayer") or
  process.executable == "memfd:spawn_worker_trampoline"
)
'''

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/"
[[threat]]
framework = "MITRE ATT&CK"

[threat.tactic]
id = "TA0011"
name = "Command and Control"
reference = "https://attack.mitre.org/tactics/TA0011/"

[internal]
min_endpoint_version = "9.1.4"