Network Activity from Memory File Descriptor

[rule]
description = """
Detects when a file descriptor in the proc (temporary) file system is executed and immediately makes an outbound network
connection. This activity can occur when the memfd syscall is utilized to create a memory resident file, like a payload,
and then execute it after which is establishes outbound network connections (C2).
"""
id = "4c8b9c6f-4d85-4fa9-9104-16f7a99aded6"
license = "Elastic License v2"
name = "Network Activity from Memory File Descriptor"
os_list = ["linux"]
reference = [
    "https://github.com/MythicAgents/merlin/blob/main/Payload_Type/merlin/container/commands/memfd.go",
    "https://x-c3ll.github.io/posts/fileless-memfd_create/",
]
version = "1.0.17"

query = '''
sequence by process.entity_id with maxspan=10s
  [process where event.type == "start" and event.action == "exec" and
  process.executable regex """/proc/(self|[0-9]{1,7})/fd/[0-9]{1,7}""" and
  not (
    process.args like ("/usr/lib/systemd/systemd-executor", "/nix/store/*/systemd-executor*") or
    process.parent.executable like (
      "/usr/sbin/runc", "/usr/bin/dockerd", "/lib/systemd/systemd", "/usr/lib/systemd/systemd", "/nix/store/*/systemd",
      "/opt/sentinelone/bin/addon-host", "/opt/gitlab/embedded/bin/gitlab-kas", "/usr/sbin/nordlayerd", "/sbin/init",
      "/proc/self/fd/*/*"
    ) or
    process.command_line == "runc init"
  )]
  [network where event.type == "start" and event.action == "connection_attempted" and
  not (
    cidrmatch(destination.ip, "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.name == "check-new-release-gtk"
  )]
'''

min_endpoint_version = "8.3.0"
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 = "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 = "8.3.0"