Performing Log Source Onboarding In Siem

Performing Log Source Onboarding in SIEM

Overview

Log source onboarding is the systematic process of integrating new data sources into a SIEM platform to enable security monitoring and detection. Proper onboarding requires planning data sources, configuring collection agents, building parsers, normalizing fields to a common schema, and validating data quality. According to the UK NCSC, onboarding should prioritize log sources that provide the highest security value relative to their ingestion cost.

When to Use

Trigger phrases:

• "performing log source onboarding in siem"

• "Perform structured log source onboarding into SIEM platforms by configuring coll"

• When conducting security assessments that involve performing log source onboarding in siem

• When following incident response procedures for related security events

• When performing scheduled security testing or auditing activities

• When validating security controls through hands-on testing

Prerequisites

• SIEM platform deployed (Splunk, Elastic, Sentinel, QRadar, or similar)
• Network access from source systems to SIEM collectors
• Administrative access on source systems for agent installation
• Common Information Model (CIM) or equivalent schema documentation
• Change management approval for production system modifications

Log Source Priority Framework

This section covers log source priority framework for performing log source onboarding in siem.

• Ensure all prerequisites are met before proceeding
• Follow the documented workflow steps in sequence
• Record results and any anomalies encountered during this phase

Tier 1 - Critical (Onboard First)

Tier 2 - High Priority

Tier 3 - Standard

Onboarding Process

1. Scope the task — define objectives, boundaries, and success criteria
2. Gather information — collect all necessary data and context before proceeding
3. Execute the core workflow — follow the domain-specific steps methodically
4. Validate results — verify outputs against expected outcomes or baselines
5. Document findings — record results, anomalies, and recommendations

Step 1: Discovery and Assessment

1. Identify the log source:
   - System type and version
   - Log format (syslog, CEF, JSON, Windows Events, etc.)
   - Log volume estimate (EPS - events per second)
   - Network location and firewall requirements

2. Assess security value:
   - What threats can this source help detect?
   - Which MITRE ATT&CK techniques does it cover?
   - Is there an existing SIEM parser?

3. Estimate ingestion cost:
   - Daily volume in GB
   - License impact (per-GB or per-EPS pricing)
   - Storage retention requirements

Step 2: Configure Log Collection

Syslog-Based Collection (Firewalls, Network Devices)

# rsyslog configuration for receiving syslog
# /etc/rsyslog.d/10-siem-collection.conf

# UDP reception
module(load="imudp")
input(type="imudp" port="514" ruleset="siem_forwarding")

# TCP reception
module(load="imtcp")
input(type="imtcp" port="514" ruleset="siem_forwarding")

# TLS reception
module(load="imtcp" StreamDriver.AuthMode="x509/name"
       StreamDriver.Mode="1" StreamDriver.Name="gtls")
input(type="imtcp" port="6514" ruleset="siem_forwarding")

ruleset(name="siem_forwarding") {
    # Forward to SIEM
    action(type="omfwd" target="siem.company.com" port="9514"
           protocol="tcp" queue.type="LinkedList"
           queue.filename="siem_fwd" queue.maxdiskspace="1g"
           queue.saveonshutdown="on" action.resumeRetryCount="-1")
}

Windows Event Log Collection (Splunk Universal Forwarder)

# inputs.conf on Splunk Universal Forwarder
[WinEventLog://Security]
disabled = 0
index = wineventlog
sourcetype = WinEventLog:Security
evt_resolve_ad_obj = 1
checkpointInterval = 5

[WinEventLog://System]
disabled = 0
index = wineventlog
sourcetype = WinEventLog:System

[WinEventLog://Microsoft-Windows-Sysmon/Operational]
disabled = 0
index = wineventlog
sourcetype = XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
renderXml = true

[WinEventLog://Microsoft-Windows-PowerShell/Operational]
disabled = 0
index = wineventlog
sourcetype = XmlWinEventLog:Microsoft-Windows-PowerShell/Operational

Cloud Log Collection (AWS CloudTrail)

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "CloudTrailToSIEM": {
      "Type": "AWS::CloudTrail::Trail",
      "Properties": {
        "TrailName": "siem-cloudtrail",
        "S3BucketName": "company-cloudtrail-logs",
        "IsLogging": true,
        "IsMultiRegionTrail": true,
        "IncludeGlobalServiceEvents": true,
        "EnableLogFileValidation": true,
        "EventSelectors": [
          {
            "ReadWriteType": "All",
            "IncludeManagementEvents": true,
            "DataResources": [
              {
                "Type": "AWS::S3::Object",
                "Values": ["arn:aws:s3"]
              }
            ]
          }
        ]
      }
    }
  }
}

Step 3: Parse and Normalize

Custom Parser Example (Splunk props.conf/transforms.conf)

# props.conf
[custom:firewall:logs]
SHOULD_LINEMERGE = false
LINE_BREAKER = ([\r\n]+)
TIME_PREFIX = ^
TIME_FORMAT = %Y-%m-%dT%H:%M:%S%z
MAX_TIMESTAMP_LOOKAHEAD = 30
TRANSFORMS-firewall = firewall_extract_fields
FIELDALIAS-src = src_addr AS src_ip
FIELDALIAS-dst = dst_addr AS dest_ip
EVAL-action = case(fw_action=="allow", "allowed", fw_action=="deny", "blocked", true(), "unknown")
EVAL-vendor_product = "Custom Firewall"
LOOKUP-geo = geo_ip_lookup ip AS dest_ip OUTPUT country, city, latitude, longitude

# transforms.conf
[firewall_extract_fields]
REGEX = ^(\S+)\s+(\S+)\s+action=(\w+)\s+src=(\S+):(\d+)\s+dst=(\S+):(\d+)\s+proto=(\w+)\s+bytes=(\d+)
FORMAT = timestamp::$1 hostname::$2 fw_action::$3 src_addr::$4 src_port::$5 dst_addr::$6 dst_port::$7 protocol::$8 bytes::$9

CIM Field Mapping

Step 4: Validate Data Quality

# Verify events are arriving
index=new_source earliest=-1h
| stats count by sourcetype, host, source

# Check field extraction quality
index=new_source earliest=-1h
| stats count(src_ip) as has_src count(dest_ip) as has_dest count(action) as has_action count by sourcetype
| eval src_coverage=round(has_src/count*100,1)
| eval dest_coverage=round(has_dest/count*100,1)
| eval action_coverage=round(has_action/count*100,1)

# Verify CIM compliance
| datamodel Network_Traffic search
| search sourcetype=new_sourcetype
| stats count by source, sourcetype

# Check for timestamp parsing issues
index=new_source earliest=-1h
| eval time_diff=abs(_time - _indextime)
| stats avg(time_diff) as avg_lag max(time_diff) as max_lag by host
| where avg_lag > 300

Step 5: Enable Detection Coverage

# Verify existing correlation searches work with new source
index=new_source sourcetype=new_sourcetype
| tstats count from datamodel=Authentication by _time span=1h
| timechart span=1h count

# Create source-specific detection rule
[New Source - Authentication Anomaly]
search = index=new_source sourcetype=new_sourcetype action=failure \
| stats count by src_ip, user \
| where count > 10

Onboarding Checklist

• Log source assessed and approved
• Network connectivity verified
• Collection agent/method configured
• Log forwarding confirmed
• Parser/field extraction configured
• CIM compliance validated
• Data model acceleration enabled
• Volume within license budget
• Retention policy configured
• Detection rules enabled/created
• Dashboard updated
• Documentation completed
• SOC team notified

When NOT to Use

• You don't have explicit written authorization to test
• Task is about defense/detection, not offense (use detection skills)
• You need to implement security controls (use implementing-* skills)
• Task requires compliance auditing (use auditing-* skills)
• You're investigating an incident (use incident response skills)
• Target is out of scope for your engagement
• Task is about vulnerability scanning only (use scanning tools)

Red Flags

• Performing actions without explicit written authorization from the asset owner
• Testing against production systems without a defined scope and rules of engagement
• Sharing sensitive findings or credentials in unencrypted communications
• Failing to properly scope and contain the assessment before starting

Verification

• All steps executed successfully against a test environment before production use
• Output documented with screenshots or logs demonstrating expected behavior
• Results validated against known-good baselines or reference implementations
• Documentation complete enough for another analyst to reproduce findings

References

• UK NCSC - Onboarding Systems and Log Sources
• Sumo Logic - Cloud SIEM Onboarding Checklist
• SIEM Logging Best Practices - Coralogix
• Huntress - SIEM Implementation Guide

Process

1. Analyze the task requirements
2. Apply domain expertise
3. Verify output quality

Anti-Rationalization Table