Unexpected File Made Executable

Detect commands used to bless a file as executable

Description

ODK (osquery-defense-kit) is unique in that the queries are designed to be used as part of a production detection & response pipeline. The detection queries are formulated to return zero rows during normal expected behavior, so that they may be configured to generate alerts when rows are returned.

Query

-- Detect commands used to bless a file as executable
--
-- false positives:
--   * none observed, but they are expected
--
-- interval: 600
-- platform: posix
-- tags: process events
SELECT
  -- Child
  pe.path AS p0_path,
  REGEX_MATCH (pe.path, '.*/(.*)', 1) AS p0_name,
  TRIM(pe.cmdline) AS p0_cmd,
  pe.cwd AS p0_cwd,
  pe.time AS p0_time,
  pe.euid AS p0_euid,
  pe.pid AS p0_pid,
  p.cgroup_path AS p0_cgroup,
  -- Parent
  pe.parent AS p1_pid,
  p1.cgroup_path AS p1_cgroup,
  TRIM(COALESCE(p1.cmdline, pe1.cmdline)) AS p1_cmd,
  COALESCE(p1.path, pe1.path) AS p1_path,
  COALESCE(p_hash1.sha256, pe_hash1.sha256) AS p1_hash,
  REGEX_MATCH (COALESCE(p1.path, pe1.path), '.*/(.*)', 1) AS p1_name,
  -- Grandparent
  COALESCE(p1.parent, pe1.parent) AS p2_pid,
  COALESCE(p1_p2.cgroup_path, pe1_p2.cgroup_path) AS p2_cgroup,
  TRIM(
    COALESCE(p1_p2.cmdline, pe1_p2.cmdline, pe1_pe2.cmdline)
  ) AS p2_cmd,
  COALESCE(p1_p2.path, pe1_p2.path, pe1_pe2.path) AS p2_path,
  COALESCE(
    p1_p2_hash.path,
    pe1_p2_hash.path,
    pe1_pe2_hash.path
  ) AS p2_hash,
  REGEX_MATCH (
    COALESCE(p1_p2.path, pe1_p2.path, pe1_pe2.path),
    '.*/(.*)',
    1
  ) AS p2_name,
  -- Extra fields
  REGEX_MATCH (TRIM(pe.cmdline), ".* (.*?)$", 1) AS target_path
FROM
  process_events pe,
  uptime
  LEFT JOIN processes p ON pe.pid = p.pid
  -- Parents (via two paths)
  LEFT JOIN processes p1 ON pe.parent = p1.pid
  LEFT JOIN hash p_hash1 ON p1.path = p_hash1.path
  LEFT JOIN process_events pe1 ON pe.parent = pe1.pid
  AND pe1.cmdline != ''
  LEFT JOIN hash pe_hash1 ON pe1.path = pe_hash1.path
  -- Grandparents (via 3 paths)
  LEFT JOIN processes p1_p2 ON p1.parent = p1_p2.pid -- Current grandparent via parent processes
  LEFT JOIN processes pe1_p2 ON pe1.parent = pe1_p2.pid -- Current grandparent via parent events
  LEFT JOIN process_events pe1_pe2 ON pe1.parent = pe1_p2.pid
  AND pe1_pe2.cmdline != '' -- Past grandparent via parent events
  LEFT JOIN hash p1_p2_hash ON p1_p2.path = p1_p2_hash.path
  LEFT JOIN hash pe1_p2_hash ON pe1_p2.path = pe1_p2_hash.path
  LEFT JOIN hash pe1_pe2_hash ON pe1_pe2.path = pe1_pe2_hash.path
WHERE
  pe.time > (strftime('%s', 'now') -600)
  AND pe.cmdline != ''
  AND pe.path IN ('/bin/chmod', '/usr/bin/chmod')
  AND (
    p0_cmd LIKE '%chmod 7%'
    OR p0_cmd LIKE '%chmod 5%'
    OR p0_cmd LIKE '%chmod 1%'
    OR p0_cmd LIKE '%chmod +%x'
  )
  AND p0_cmd NOT LIKE 'chmod 700 /tmp/apt-key-gpghome.%'
  AND p0_cmd NOT LIKE 'chmod 700 /home/%/snap/%/.config'
  AND p0_cmd NOT LIKE 'chmod 755 /home/%/.gradle/wrapper/dists/gradle-%-bin/%bin/gradle'
  AND p0_cmd NOT IN ('chmod 755 /usr/local/share/ca-certificates')
  AND NOT p0_cgroup LIKE '/system.slice/docker-%'
GROUP BY
  pe.pid

tags: SStagSS

Reference

https://github.com/chainguard-dev/osquery-defense-kit