From c7fe940206d6646721dd448666d563ae7fb63bb7 Mon Sep 17 00:00:00 2001
From: Ruben Groenewoud <78494512+Aegrah@users.noreply.github.com>
Date: Fri, 3 Jan 2025 14:35:08 +0100
Subject: [PATCH] [New Rule] Pluggable Authentication Module Creation in
 Unusual Directory (#4302)

* [New Rule] Pluggable Authentication Module Creation in Unusual Directory

* Update persistence_pluggable_authentication_module_creation_in_unusual_dir.toml

* Update rules/linux/persistence_pluggable_authentication_module_creation_in_unusual_dir.toml
---
 ...cation_module_creation_in_unusual_dir.toml | 82 +++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 rules/linux/persistence_pluggable_authentication_module_creation_in_unusual_dir.toml

diff --git a/rules/linux/persistence_pluggable_authentication_module_creation_in_unusual_dir.toml b/rules/linux/persistence_pluggable_authentication_module_creation_in_unusual_dir.toml
new file mode 100644
index 000000000..34f323e74
--- /dev/null
+++ b/rules/linux/persistence_pluggable_authentication_module_creation_in_unusual_dir.toml
@@ -0,0 +1,82 @@
+[metadata]
+creation_date = "2024/12/16"
+integration = ["endpoint"]
+maturity = "production"
+updated_date = "2024/12/16"
+
+[rule]
+author = ["Elastic"]
+description = """
+This rule detects the creation of Pluggable Authentication Module (PAM) shared object files in unusual directories.
+Attackers may compile PAM shared object files in temporary directories, to move them to system directories later,
+potentially allowing them to maintain persistence on a compromised system, or harvest account credentials.
+"""
+false_positives = [
+    "Trusted system module updates or allowed Pluggable Authentication Module (PAM) daemon configuration changes.",
+]
+from = "now-9m"
+index = ["logs-endpoint.events.file*"]
+language = "eql"
+license = "Elastic License v2"
+name = "Pluggable Authentication Module (PAM) Creation in Unusual Directory"
+references = [
+    "https://github.com/zephrax/linux-pam-backdoor",
+    "https://github.com/eurialo/pambd",
+    "http://0x90909090.blogspot.com/2016/06/creating-backdoor-in-pam-in-5-line-of.html",
+    "https://www.trendmicro.com/en_us/research/19/i/skidmap-linux-malware-uses-rootkit-capabilities-to-hide-cryptocurrency-mining-payload.html",
+]
+risk_score = 21
+rule_id = "5c832156-5785-4c9c-a2e7-0d80d2ba3daa"
+severity = "low"
+tags = [
+    "Domain: Endpoint",
+    "OS: Linux",
+    "Use Case: Threat Detection",
+    "Tactic: Credential Access",
+    "Tactic: Persistence",
+    "Data Source: Elastic Defend",
+]
+timestamp_override = "event.ingested"
+type = "eql"
+query = '''
+file where host.os.type == "linux" and event.type == "creation" and file.name like "pam_*.so" and not file.path like (
+  "/lib/security/*",
+  "/lib64/security/*",
+  "/lib/x86_64-linux-gnu/security/*",
+  "/usr/lib/security/*",
+  "/usr/lib64/security/*",
+  "/usr/lib/x86_64-linux-gnu/security/*"
+) and not (
+  process.name in ("dockerd", "containerd", "steam", "buildkitd", "unsquashfs", "pacman") or
+  file.path like (
+    "/build/rootImage/nix/store/*", "/home/*/.local/share/containers/*", "/nix/store/*", "/var/lib/containerd/*",
+    "/var/snap/*", "/usr/share/nix/nix/store/*", "/tmp/cura/squashfs-root/*", "/home/*/docker/*", "/tmp/containerd*"
+  )
+)
+'''
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1543"
+name = "Create or Modify System Process"
+reference = "https://attack.mitre.org/techniques/T1543/"
+
+[rule.threat.tactic]
+id = "TA0003"
+name = "Persistence"
+reference = "https://attack.mitre.org/tactics/TA0003/"
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1556"
+name = "Modify Authentication Process"
+reference = "https://attack.mitre.org/techniques/T1556/"
+
+[rule.threat.tactic]
+id = "TA0006"
+name = "Credential Access"
+reference = "https://attack.mitre.org/tactics/TA0006/"