new detector: unexpected process extension linux

detection/evasion/unexpected-process-extension-linux.sql

@@ -0,0 +1,56 @@
+-- Processes that have an unusual extension
+--
+-- false positives:
+--   * none observed
+--
+-- references:
+--   * https://www.uptycs.com/blog/new-poc-exploit-backdoor-malware
+--
+-- tags: persistent process state
+-- platform: linux
+
+SELECT
+  -- Child
+  p0.pid AS p0_pid,
+  p0.path AS p0_path,
+  p0.name AS p0_name,
+  p0.start_time AS p0_start,
+  p0.cmdline AS p0_cmd,
+  p0.cwd AS p0_cwd,
+  REGEX_MATCH (p0.path, '.*\/(.*?)$', 1) AS basename,
+  REGEX_MATCH (p0.path, '.*\.(\w+)$', 1) AS extension,
+  p0.cgroup_path AS p0_cgroup,
+  p0.euid AS p0_euid,
+  p0_hash.sha256 AS p0_sha256,
+  -- Parent
+  p0.parent AS p1_pid,
+  p1.path AS p1_path,
+  p1.name AS p1_name,
+  p1.start_time AS p1_start,
+  p1.euid AS p1_euid,
+  p1.cmdline AS p1_cmd,
+  p1_hash.sha256 AS p1_sha256,
+  -- Grandparent
+  p1.parent AS p2_pid,
+  p2.name AS p2_name,
+  p2.start_time AS p2_start,
+  p2.path AS p2_path,
+  p2.cmdline AS p2_cmd,
+  p2_hash.sha256 AS p2_sha256
+FROM
+  processes p0
+  LEFT JOIN hash p0_hash ON p0.path = p0_hash.path
+  LEFT JOIN processes p1 ON p0.parent = p1.pid
+  LEFT JOIN hash p1_hash ON p1.path = p1_hash.path
+  LEFT JOIN processes p2 ON p1.parent = p2.pid
+  LEFT JOIN hash p2_hash ON p2.path = p2_hash.path
+WHERE
+  extension IS NOT NULL
+  AND extension NOT IN (
+    '1',
+    '2',
+    'real',
+    'ext'
+  )
+  AND NOT basename LIKE 'python3.%'
+  AND NOT basename LIKE 'python2.%'