Ansible Linux Security Logging Stack

This Ansible project prepares Linux servers to forward security-focused logs (Sysmon for Linux and Auditd) to a remote SIEM using Rsyslog.

Overview

This repository contains an Ansible project that installs and configures a minimal but highly effective Linux security logging stack. The configuration is optimized to reduce noise by leveraging the strengths of each tool:

• Sysmon for Linux: Handles high-volume operational data (Process execution, Network connections, File operations).
• Auditd: Focuses on sensitive configuration changes, persistence mechanisms, and system integrity (FIM).
• Rsyslog: Forwards combined logs to a remote SIEM over TCP/UDP/RELP.

Detection Capabilities

Based on the applied configurations, the following events are captured:

1. Sysmon for Linux (Operational Visibility)

Event ID	Name	Description
1	Process Create	Logs process starts. Optimized: Excludes noisy system processes (cron, monit, splunkd).
3	Network Connect	Logs network connections. Optimized: Excludes localhost/loopback traffic.
5	Process Terminate	(Disabled/Empty) Low value for general monitoring.
9	RawAccessRead	(Disabled) High noise volume.
11	File Create	Logs file creation in critical paths only (/etc, /boot, /bin, /var/www).
23	File Delete	Logs file deletion in critical paths only (/etc, /boot, /var/log).

2. Auditd (Compliance & Integrity)

Specific rules are configured to detect changes in critical system areas. Note that standard process execution (execve) logging is disabled in Auditd to avoid overlap with Sysmon Event ID 1.

• Identity & Authentication:
  • Modifications to /etc/passwd, /etc/shadow, /etc/group.
  • Changes to Sudoers (/etc/sudoers, /etc/sudoers.d).
  • Execution of sudo and passwd binaries.
  • PAM configuration changes.
• System Integrity & Persistence:
  • Kernel Modules: Loading/Unloading (insmod, rmmod, modprobe).
  • Systemd: Changes to unit files in /etc/systemd/system and /lib/systemd/system.
  • Cron: Modifications to crontab and cron directories.
  • Mounts: Execution of mount command and changes to /etc/fstab.
• Network Configuration:
  • Hostname/Domain name changes.
  • Modifications to /etc/hosts and /etc/NetworkManager.
• Package Management:
  • Execution of rpm, yum, dnf, dpkg, apt.
  • Writes to package manager logs (dpkg.log, yum.log).
• Suspicious Activity:
  • Ptrace: Detection of process injection attempts.
  • System State: Usage of shutdown, reboot, poweroff.

Quick Start

1. Configure SIEM Connection

Edit group_vars/all.yml to set your remote log destination:

siem_host: "192.168.1.50"
siem_port: "514"
siem_protocol: "tcp" # or udp

2. Run the Playbook

Run the main playbook against your inventory:

Bash

ansible-playbook -i inventory/hosts.ini playbooks/site.yml

Test & Verification

Apply the playbook to a test host first, then verify the stack is running and capturing events.

Service Checks (On Target Host)

Bash

# Check Sysmon status (Service name: sysmon)
sudo systemctl status sysmon

# Check Auditd rules are loaded
sudo auditctl -l

# Check Rsyslog status
sudo systemctl status rsyslog

Generate Test Events

Execute the following commands on the target host to trigger specific rules:

Bash

# Trigger: Sysmon ProcessCreate (ID 1) & Auditd Package Mgmt
sudo apt-get update 

# Trigger: Auditd Network Config & Sysmon FileCreate (ID 11)
sudo touch /etc/NetworkManager/test_alert

# Trigger: Auditd Persistence (Systemd) & Sysmon FileCreate
sudo bash -c 'echo "[Unit]" > /etc/systemd/system/malicious.service'

# Trigger: Sysmon NetworkConnect (ID 3)
curl -I [https://www.google.com](https://www.google.com)

# Trigger: Auditd Identity Change
sudo touch /etc/sudoers.d/test_privesc

# Trigger: Auditd Ptrace (Injection)
strace ls

Check Local Logs

Verify that logs are being generated locally before checking the SIEM:

Bash

# Check recent Sysmon logs (via Journal)
sudo journalctl -u sysmon -n 20 --no-pager

# Check recent Auditd logs (via ausearch)
sudo ausearch -m CONFIG_CHANGE,SYSCALL -ts recent

Production Notes

• Sensitive Variables: Always use Ansible Vault for sensitive data (e.g., SIEM credentials if used).

• Performance: Sysmon Event ID 11 (FileCreate) and ID 23 (FileDelete) on * (all files) can be noisy on high-traffic file servers or database servers. Tune the sysmon-config.xml if necessary.

• Privileges: The rsyslog service is configured with ACLs to read /var/log/audit/audit.log without running as full root (if configured via ACL method).### 2. Run the Playbook

Run the main playbook against your inventory:

Bash

ansible-playbook -i inventory/hosts.ini playbooks/site.yml

Test & Verification

Apply the playbook to a test host first, then verify the stack is running and capturing events.

Service Checks (On Target Host)

Bash

# Check Sysmon status (Service name: sysmon)
sudo systemctl status sysmon

# Check Auditd rules are loaded
sudo auditctl -l

# Check Rsyslog status
sudo systemctl status rsyslog

Generate Test Events

Execute the following commands on the target host to trigger specific rules:

Bash

# Trigger: Sysmon ProcessCreate (ID 1) & Auditd Package Mgmt
sudo apt-get update 

# Trigger: Auditd Network Config & Sysmon FileCreate (ID 11)
sudo touch /etc/NetworkManager/test_alert

# Trigger: Auditd Persistence (Systemd) & Sysmon FileCreate
sudo bash -c 'echo "[Unit]" > /etc/systemd/system/malicious.service'

# Trigger: Sysmon NetworkConnect (ID 3)
curl -I [https://www.google.com](https://www.google.com)

# Trigger: Auditd Identity Change
sudo touch /etc/sudoers.d/test_privesc

# Trigger: Auditd Ptrace (Injection)
strace ls

Check Local Logs

Verify that logs are being generated locally before checking the SIEM:

Bash

# Check recent Sysmon logs (via Journal)
sudo journalctl -u sysmon -n 20 --no-pager

# Check recent Auditd logs (via ausearch)
sudo ausearch -m CONFIG_CHANGE,SYSCALL -ts recent

Production Notes

• Sensitive Variables: Always use Ansible Vault for sensitive data (e.g., SIEM credentials if used).

• Performance: Sysmon Event ID 11 (FileCreate) and ID 23 (FileDelete) on * (all files) can be noisy on high-traffic file servers or database servers. Tune the sysmon-config.xml if necessary.

• Privileges: The rsyslog service is configured with ACLs to read /var/log/audit/audit.log without running as full root (if configured via ACL method).