Complete Fortinet Firewall Monitoring Guide: Log Analysis
Chaitanya Sistla
May 11, 2025
8 min read
Introduction: The Critical Need for Fortinet Monitoring
Maintaining visibility into your network security infrastructure is no longer optional, it's imperative. Fortinet firewalls stand at the frontline of your organization's defense, filtering traffic, blocking threats, and safeguarding critical assets. However, without proper monitoring, these powerful security appliances can become blind spots in your security posture.
Fortinet devices generate a wealth of security intelligence through their logs by capturing everything from connection attempts and policy matches to potential intrusions and performance metrics. These logs hold the key to understanding your security posture, identifying emerging threats, and ensuring compliance with security frameworks. When these logs remain unmonitored or underutilized, organizations miss critical security insights that could prevent breaches, data loss, or service disruptions.
Effective Fortinet monitoring brings multiple benefits:
- Threat Detection: Identify unusual patterns, unauthorized access attempts, and potential security breaches in real-time
- Performance Optimization: Track resource utilization, throughput, and latency to ensure optimal firewall performance
- Compliance Documentation: Generate the necessary audit trails for regulatory requirements like PCI DSS, HIPAA, or SOC2
- Incident Response: Reduce mean time to detect (MTTD) and mean time to respond (MTTR) to security incidents
- Security Posture Improvement: Analyze historical data to identify recurring patterns and strengthen security policies
OpenObserve provides a comprehensive solution to unlock these benefits, transforming raw Fortinet logs into actionable security intelligence. This platform's cloud-native architecture offers scalable ingestion, processing, and visualization capabilities—handling everything from small deployments to enterprise-scale Fortinet implementations generating terabytes of daily log data.
This guide walks you through the complete process of implementing a Fortinet monitoring system using OpenObserve, from configuring log collection to building insightful dashboards. By following these steps, you'll establish continuous visibility into your Fortinet infrastructure, enabling proactive security monitoring and rapid response to potential threats.
Prerequisites
Before starting, ensure you have:
- A running Fortinet firewall
- A server to install Fluent Bit (for log collection)
- Access to an OpenObserve instance
- Basic knowledge of networking and Linux administration
Step 1: Setting Up the Syslog Server with Fluent Bit
Fluent Bit serves as an efficient log processor that will collect logs from your Fortinet devices and forward them to OpenObserve.
Installation
First, install Fluent Bit on your designated server:
# For Debian/Ubuntu
curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh
# For RHEL/CentOS
curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh
Configuration
Create the main configuration file at /etc/fluent-bit/fluent-bit.conf:
[SERVICE]
Flush 5
Daemon Off
Log_Level debug
Parsers_File parsers.conf
[INPUT]
Name syslog
Listen 0.0.0.0
Port 514
Mode udp
Parser fortinet-cef
Tag fortinet
[OUTPUT]
Name http
Match fortinet
URI /api/default/fortinet_fw_syslog/_json
Host <your-openobserve-instance>
Port 443
tls On
Format json
Json_date_key _timestamp
Json_date_format iso8601
HTTP_User <your-username>
HTTP_Passwd <your-password>
compress gzip
Create a custom parser configuration at /etc/fluent-bit/parsers.conf:
[PARSER]
Name fortinet-cef
Format regex
Regex ^\<(?<pri>[0-9]+)\>(?<time>[^ ]+ [^ ]+ [^ ]+) (?<host>[^ ]+) (?<message>.+)$
Time_Key time
Time_Format %b %d %H:%M:%S
Time_Keep On
Start Fluent Bit Service
sudo systemctl enable fluent-bit
sudo systemctl start fluent-bit
Verify it's running properly:
sudo systemctl status fluent-bit
Step 2: Configure Fortinet to Send Logs to Syslog
Now that our syslog server is ready, we need to configure the Fortinet firewall to send logs to it.
- Log into your FortiGate web interface
- Navigate to Log & Report > Log Settings
- Enable logging for the events you want to monitor
- Under Remote Logging and Archiving, add a new server:
- Set Type to "Syslog"
- Enter the IP address of your Fluent Bit server
- Set the port to 514
- Select the appropriate log levels and types
For more detailed instructions, refer to the official Fortinet documentation.
Step 3: Setting Up Data Transformation in OpenObserve
Once logs are flowing into OpenObserve, we need to transform them into a more usable format for analysis. We'll use VRL (Vector Remap Language) functions for this purpose.
Create VRL Functions
In the OpenObserve UI, navigate to Settings > Functions and create the following VRL functions:
- First function for parsing CEF format - Name it
syslog_cef:
. = merge(., {"cef": parse_cef!(.message)})
.
- Second function for IP geolocation enrichment - Name it
fortinet_ip_to_geo:
# Ensure 'publicip' exists and is a valid IP address (IPv4 or IPv6)
if exists(.cef_dst) && (is_ipv4(string!(.cef_dst)) || is_ipv6(string!(.cef_dst))) {
# Perform GeoIP enrichment using the MaxMind City database
.geo_city_data = get_enrichment_table_record!("maxmind_city", {"ip": string!(.cef_dst)})
# Extract specific fields from the city data if enrichment is successful
if exists(.geo_city_data) {
.geo_city = .geo_city_data.city
.geo_country = .geo_city_data.country
.geo_latitude = .geo_city_data.latitude
.geo_longitude = .geo_city_data.longitude
# Optionally delete the raw geo_city_data field to clean up
del(.geo_city_data)
}
# Perform GeoIP enrichment using the MaxMind ASN database
.geo_asn_data = get_enrichment_table_record!("maxmind_asn", {"ip": string!(.cef_dst)})
# Extract specific fields from the ASN data if enrichment is successful
if exists(.geo_asn_data) {
.geo_asn = .geo_asn_data.asn
.geo_org = .geo_asn_data.organization
}
}
.
Create Processing Pipeline
Next, create a pipeline that applies these functions to your incoming Fortinet logs:
- Navigate to Settings > Pipelines
- Create a new pipeline for the
fortinet_fw_syslogstream - Add the
syslog_ceffunction as the first stage - Add the
fortinet_ip_to_geofunction as the second stage - Save and activate the pipeline
Note for OpenObserve v14.6.8+ Users: If you're running OpenObserve version 14.6.8 or higher, you can simply upload the pipeline configuration file directly through the UI instead of manually creating the pipeline. Navigate to Pipelines > Import and upload your JSON pipeline fortinet_firewall_cef.json file to instantly configure your data transformation workflow.
Step 4: Creating Dashboards for Visualization
With logs flowing in and properly transformed, you can now create insightful dashboards in OpenObserve.
- Navigate to Dashboards > New Dashboard
- Create a dashboard with the following panels:
- Traffic Overview: Shows overall traffic patterns by time
- Top Source IPs: Displays the most common source IP addresses
- Top Destination IPs: Shows the most common destination IP addresses
- Geographic Distribution: Maps showing where traffic is coming from
- Blocked Traffic: Displays rejected connection attempts
- Security Events: Shows critical security alerts
- Performance Metrics: Displays firewall performance data
You can import a pre-configured dashboard by uploading a JSON template Fortinet.dashboard.json through the Import option.
Make sure to replace the stream name from fortinet_fw_syslog to your custom name that you might have configured.
Step 5: Setting Up Alerts
To proactively monitor your Fortinet firewalls, set up alerts in OpenObserve:
- Navigate to Alerts > Create Alert
- Create alerts for critical conditions such as:
- High volume of rejected connections
- Connection attempts from unusual geographic locations
- Critical security events from the firewall
- Unusual traffic patterns or spikes
Step 6: Monitoring Logs
To monitor the logs, you can go to the logs console and search for your stream that has fortinet logs.
Comparison: Monitoring Fortinet With vs. Without OpenObserve
| Feature | Without OpenObserve | With OpenObserve |
|---|---|---|
| Log Collection | Manual export or basic syslog | Automated, real-time collection via Fluent Bit |
| Storage | Limited local storage or third-party tools | Scalable, object storage |
| Data Processing | Limited or requires custom scripts | Advanced processing with VRL functions |
| Geo-enrichment | Not available or requires additional tools | Built-in geo-enrichment capabilities |
| Visualization | Basic or requires additional software | Customizable, real-time dashboards |
| Search Capability | Limited text search | Full-text search with complex queries |
| Alerting | Basic or none | Advanced alerting with multiple conditions |
| Historical Analysis | Limited by storage | Extended retention with efficient compression |
| Cost | Often requires multiple paid tools | Single platform, often more cost-effective |
| Setup Complexity | Multiple systems to integrate | Unified platform with streamlined setup |
| Performance Impact | Can be resource-intensive | Optimized for high-performance log processing |
Conclusion
Monitoring Fortinet firewalls with OpenObserve provides a comprehensive solution for security observability. By following this guide, you've set up a complete monitoring system that collects logs from your Fortinet devices, processes them for better insights, and visualizes the data in intuitive dashboards.
This approach not only enhances your security posture but also simplifies the monitoring process, allowing you to focus on addressing security concerns rather than managing log infrastructure. The real-time nature of the system ensures you stay ahead of potential threats, while the historical data enables trend analysis and security posture improvement over time.
With this setup, you'll be well-equipped to monitor, analyze, and respond to security events across your Fortinet infrastructure, turning raw log data into actionable security intelligence.
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