Agent Skills: Deploying Osquery for Endpoint Monitoring

Deploying Osquery for Endpoint Monitoring

When to Use

Use this skill when:

• Deploying osquery across Windows, macOS, and Linux endpoints for fleet-wide visibility
• Building threat hunting queries using osquery's SQL interface
• Monitoring endpoint compliance (installed software, open ports, running services)
• Integrating osquery data with SIEM or Kolide/Fleet for centralized management

Do not use for real-time alerting (osquery is periodic/on-demand; use EDR for real-time).

Prerequisites

• Osquery package for target OS (https://osquery.io/downloads)
• Fleet management server (Kolide Fleet or FleetDM) for enterprise deployment
• TLS certificates for secure agent-to-server communication
• Log aggregation pipeline (Filebeat, Fluentd) for osquery result logs

Workflow

Step 1: Install Osquery

# Ubuntu/Debian
export OSQUERY_KEY=1484120AC4E9F8A1A577AEEE97A80C63C9D8B80B
apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys $OSQUERY_KEY
add-apt-repository 'deb [arch=amd64] https://pkg.osquery.io/deb deb main'
apt-get update && apt-get install osquery -y

# Windows (MSI)
# Download from https://osquery.io/downloads/official
msiexec /i osquery-5.12.1.msi /quiet

# macOS
brew install osquery

Step 2: Configure Osquery

// /etc/osquery/osquery.conf (Linux/macOS) or C:\ProgramData\osquery\osquery.conf
{
  "options": {
    "config_plugin": "filesystem",
    "logger_plugin": "filesystem",
    "logger_path": "/var/log/osquery",
    "disable_logging": "false",
    "schedule_splay_percent": "10",
    "events_expiry": "3600",
    "verbose": "false",
    "worker_threads": "2",
    "enable_monitor": "true",
    "disable_events": "false",
    "disable_audit": "false",
    "audit_allow_config": "true",
    "host_identifier": "hostname",
    "enable_syslog": "true"
  },
  "schedule": {
    "process_monitor": {
      "query": "SELECT pid, name, path, cmdline, uid, parent FROM processes WHERE on_disk = 0;",
      "interval": 300,
      "description": "Detect processes running without on-disk binary (fileless)"
    },
    "listening_ports": {
      "query": "SELECT DISTINCT p.name, p.path, lp.port, lp.protocol, lp.address FROM listening_ports lp JOIN processes p ON lp.pid = p.pid WHERE lp.port != 0;",
      "interval": 600,
      "description": "Monitor listening network ports"
    },
    "persistence_check": {
      "query": "SELECT name, path, source FROM startup_items;",
      "interval": 3600,
      "description": "Monitor persistence mechanisms"
    },
    "installed_packages": {
      "query": "SELECT name, version, source FROM deb_packages;",
      "interval": 86400,
      "description": "Daily software inventory"
    },
    "users_and_groups": {
      "query": "SELECT u.username, u.uid, u.gid, u.shell, u.directory FROM users u WHERE u.uid >= 1000;",
      "interval": 3600
    },
    "crontab_monitor": {
      "query": "SELECT * FROM crontab;",
      "interval": 3600,
      "description": "Monitor scheduled tasks"
    },
    "suid_binaries": {
      "query": "SELECT path, username, permissions FROM suid_bin;",
      "interval": 86400,
      "description": "Detect SUID binaries"
    }
  },
  "packs": {
    "incident-response": "/usr/share/osquery/packs/incident-response.conf",
    "ossec-rootkit": "/usr/share/osquery/packs/ossec-rootkit.conf",
    "vuln-management": "/usr/share/osquery/packs/vuln-management.conf"
  }
}

Step 3: Threat Hunting Queries

-- Detect processes with no on-disk binary (potential fileless malware)
SELECT pid, name, path, cmdline FROM processes WHERE on_disk = 0;

-- Find listening ports not associated with known services
SELECT lp.port, lp.protocol, p.name, p.path
FROM listening_ports lp JOIN processes p ON lp.pid = p.pid
WHERE lp.port NOT IN (22, 80, 443, 3306, 5432);

-- Detect unauthorized SSH keys
SELECT * FROM authorized_keys WHERE NOT key LIKE '%admin-team%';

-- Find recently modified system binaries
SELECT path, mtime, size FROM file
WHERE path LIKE '/usr/bin/%' AND mtime > (strftime('%s', 'now') - 86400);

-- Detect processes connecting to external IPs
SELECT DISTINCT p.name, p.path, pn.remote_address, pn.remote_port
FROM process_open_sockets pn JOIN processes p ON pn.pid = p.pid
WHERE pn.remote_address NOT LIKE '10.%'
  AND pn.remote_address NOT LIKE '172.16.%'
  AND pn.remote_address NOT LIKE '192.168.%'
  AND pn.remote_address != '127.0.0.1'
  AND pn.remote_address != '0.0.0.0';

-- Windows: Detect unsigned running executables
SELECT p.name, p.path, a.result AS signature_status
FROM processes p JOIN authenticode a ON p.path = a.path
WHERE a.result != 'trusted';

Step 4: Deploy FleetDM for Centralized Management

# FleetDM provides centralized osquery management
# Deploy FleetDM server, configure agents to report to it
# Agents use TLS enrollment and config from Fleet

# Agent configuration for Fleet:
# --tls_hostname=fleet.corp.com
# --tls_server_certs=/etc/osquery/fleet.pem
# --enroll_secret_path=/etc/osquery/enroll_secret

Key Concepts

| Term | Definition | |------|-----------| | Osquery | Open-source endpoint agent that exposes OS state as SQL tables for querying | | Schedule | Periodic queries that run at defined intervals and log results | | Pack | Collection of related queries grouped for specific use cases (IR, compliance) | | FleetDM | Open-source osquery fleet management platform | | Differential Results | Osquery logs only changes between query executions, reducing data volume |

Tools & Systems

• Osquery: https://osquery.io/ - endpoint visibility agent
• FleetDM: https://fleetdm.com/ - centralized fleet management
• Kolide: Cloud-based osquery management with Slack integration
• osquery-go: Go client library for osquery extensions

Common Pitfalls

• Query performance: Complex queries with large table scans impact endpoint performance. Use WHERE clauses and test query cost with EXPLAIN.
• Schedule intervals too aggressive: Running heavy queries every 60 seconds causes CPU spikes. Use 300-3600 second intervals for most queries.
• Not using differential mode: Without differential logging, osquery logs all results every interval. Differential mode logs only changes.
• Missing event tables: Some osquery tables require events framework enabled (process_events, socket_events). Enable with --disable_events=false.