Part of the Cybersecurity Skills Guide — This article is one deep-dive in our complete skills and certifications series.

SIEM Tools Explained: Splunk, QRadar, ELK

By HADESS Team | February 28, 2026 | Updated: February 28, 2026 | 11 min read

Table of Contents

• What Is a SIEM and Why It Matters
• How SIEM Works: Core Architecture
• Splunk Enterprise Security
• IBM QRadar
• ELK Stack (Elastic Security)
• Microsoft Sentinel
• Feature Comparison Table
• Query Languages: SPL vs KQL vs Lucene vs AQL
• Which SIEM Should You Learn?
• SIEM Career Value and Job Market
• Getting Hands-On: Free SIEM Labs
• Frequently Asked Questions

What Is a SIEM and Why It Matters

A SIEM tools comparison starts with understanding what a SIEM does and why organizations invest heavily in these platforms. SIEM (Security Information and Event Management) collects log data from across an organization’s infrastructure, normalizes it into a common format, correlates events to identify threats, and provides the interface through which analysts detect and investigate security incidents.

Without a SIEM, security teams would need to manually check logs on individual firewalls, servers, endpoints, and applications. In an environment generating millions of events per day, manual review is impossible. The SIEM centralizes this data and applies rules, statistical analysis, and machine learning to surface the events that warrant investigation.

SIEM platforms serve as the operational hub of a Security Operations Center (SOC). They are where analysts spend most of their working hours. Understanding how SIEMs function — and gaining proficiency in at least one platform — is a foundational skill for anyone entering cybersecurity.

For context on how SIEM skills fit alongside other security competencies, see the cybersecurity skills guide and our breakdown of top cybersecurity skills employers want.

How SIEM Works: Core Architecture

Every SIEM, regardless of vendor, follows a similar architectural pattern:

1. Data collection: Log sources send data to the SIEM. Sources include firewalls, IDS/IPS, endpoints (via agents), servers, applications, cloud services, DNS servers, proxy servers, and authentication systems. Data arrives via syslog, API ingestion, file monitoring, or vendor-specific agents.

2. Parsing and normalization: Raw logs come in hundreds of different formats. The SIEM parses each format and maps fields to a common schema. A firewall log and a Windows Event Log both contain a “source IP” — normalization ensures both map to the same field name for consistent querying.

3. Indexing and storage: Normalized events are indexed for fast search and stored for retention requirements. Storage architecture varies: Splunk uses proprietary indexing, Elastic uses Lucene-based indexing, QRadar uses Ariel database. Storage costs are a primary budget concern — ingesting 500GB of logs per day at $3/GB adds up fast.

4. Correlation and detection: Rules compare events against known attack patterns. A single failed login is noise. Five hundred failed logins from the same IP against different accounts in ten minutes is a brute force attack. Correlation rules define these patterns and generate alerts.

5. Alerting and investigation: When correlation rules trigger, analysts receive alerts. The SIEM provides investigation tools: search, drill-down, timeline views, and integration with threat intelligence. Analysts determine whether alerts represent true threats or false positives.

6. Reporting and compliance: Automated reports satisfy regulatory requirements (PCI DSS, HIPAA, SOX). Dashboards provide operational visibility to security leadership.

Splunk Enterprise Security

Splunk is the market leader in SIEM and log management. Its strength lies in its search processing language (SPL), which provides powerful and flexible data analysis capabilities.

Strengths:

• SPL is the most expressive SIEM query language. It handles everything from simple searches to statistical analysis, time-series correlation, and machine learning
• Massive ecosystem of apps and add-ons in Splunkbase (marketplace)
• Strong community support and extensive documentation
• Flexible deployment: on-premises, cloud (Splunk Cloud), or hybrid
• Enterprise Security (ES) app adds pre-built security dashboards, notable events framework, and risk-based alerting

Weaknesses:

• Expensive. Pricing is based on data ingestion volume, and costs scale rapidly
• Steep learning curve for advanced SPL
• Resource-intensive infrastructure requirements for on-premises deployment
• License management complexity

SPL example — Find brute force SSH attempts:
“
index=linux sourcetype=syslog "Failed password"
| stats count by src_ip, dest_ip
| where count > 10
| sort -count
`

AQL example — Find brute force login attempts:
`sql
SELECT sourceip, COUNT(*) as attempt_count
FROM events
WHERE category = 'Authentication'
AND outcome = 'Failure'
GROUP BY sourceip
HAVING COUNT(*) > 10
ORDER BY attempt_count DESC
LAST 1 HOURS
`

KQL example — Find brute force SSH attempts:
`
event.category: "authentication" AND event.outcome: "failure"
AND process.name: "sshd"
`

KQL example — Find brute force sign-in attempts:
`
SigninLogs
| where ResultType != 0
| summarize FailureCount=count() by IPAddress
| where FailureCount > 10
| sort by FailureCount desc
“

Market position: Growing rapidly. Organizations already in the Microsoft ecosystem often choose Sentinel because it eliminates the need for a separate SIEM vendor. Appearing in an increasing number of job postings, particularly for cloud-focused security roles.

Feature Comparison Table

Query Languages: SPL vs KQL vs Lucene vs AQL

The query language is your primary interface with a SIEM. Proficiency in at least one is expected for any SOC analyst role.

SPL (Search Processing Language) — Splunk: Pipe-based syntax similar to Unix command chaining. Start with a search, pipe results through transforming commands (stats, eval, table, chart). Most powerful and flexible, but longest learning curve.

KQL (Kusto Query Language) — Microsoft Sentinel and some Elastic features: Tabular, SQL-like syntax. Data flows through operators (where, summarize, project, join). Readable and well-documented. Increasingly valuable as Sentinel adoption grows.

Lucene/KQL — Elastic: Elasticsearch supports both Lucene query syntax (for simple searches) and KQL in Kibana. Lucene uses field:value syntax with boolean operators. KQL adds user-friendly syntax on top.

AQL (Ariel Query Language) — QRadar: SQL-like syntax querying QRadar’s Ariel database. Familiar to anyone who knows SQL. Less flexible than SPL for complex transformations.

Recommendation: If you are starting fresh, learn SPL or Kusto KQL first. SPL has the broadest market applicability. Kusto KQL is growing fastest and transfers between Sentinel and Azure Data Explorer. Once you know one query language well, adapting to others takes weeks, not months.

Which SIEM Should You Learn?

Your choice should depend on three factors:

1. Your target employers: Research the SIEM platforms used by companies you want to work for. Job postings often list specific SIEM experience. If five of your target companies use Splunk, learn Splunk.

2. Your access to free resources: ELK Stack is the easiest to set up at home with no cost. Splunk Free limits you to 500MB/day but is fully functional. Sentinel requires an Azure subscription (free trial available).

3. Your career direction:

• SOC Analyst: Splunk (broadest demand) or Sentinel (if targeting Microsoft shops)
• Detection Engineer: Elastic Security (open-source detection rules) or Splunk (SPL power)
• Cloud Security: Sentinel (Microsoft environment) or Elastic (multi-cloud)
• Government/Defense: QRadar or Splunk (common in federal environments)

Learn the concepts (data ingestion, normalization, correlation, alerting) in any platform. The concepts transfer across all SIEMs. Platform-specific syntax can be learned quickly once you understand the underlying principles.

For deeper coverage of network-level monitoring that feeds into SIEM platforms, see our network security fundamentals guide.

SIEM Career Value and Job Market

SIEM proficiency directly impacts employability and earning potential for security analysts.

Entry-level positions (SOC Analyst Tier 1): Employers expect familiarity with at least one SIEM. You should be able to search logs, read alerts, and investigate basic incidents. Demonstrating Splunk or Sentinel skills in an interview gives you a measurable advantage.

Mid-career positions (SOC Analyst Tier 2-3, Detection Engineer): Deep SIEM expertise becomes a primary hiring criterion. Employers expect you to write correlation rules, tune detection logic, onboard new log sources, and build dashboards. Knowing multiple SIEMs is valuable at this level.

Senior positions (SOC Manager, Security Architect): SIEM selection, deployment architecture, and performance optimization. Understanding the strengths and limitations of different platforms enables informed technology decisions.

Salary impact: SOC analysts with demonstrated SIEM proficiency (certifications or verifiable experience) typically command 10-20% higher salaries than those without. Splunk certifications show the strongest correlation with salary premiums.

Explore how SIEM skills connect with zero trust security and threat intelligence in our related guides.

Getting Hands-On: Free SIEM Labs

Splunk Free:
1. Download Splunk Free (500MB/day ingestion limit)
2. Install on a VM or local machine
3. Ingest sample data from Splunk’s Boss of the SOC (BOTS) dataset
4. Complete the free Splunk Fundamentals 1 course

Elastic Security:
1. Install Elasticsearch and Kibana (free Basic license)
2. Deploy Elastic Agent on lab machines
3. Enable built-in detection rules
4. Ingest logs from a pfSense firewall and a web server in your lab

Microsoft Sentinel:
1. Create an Azure free trial account
2. Deploy a Sentinel workspace
3. Connect free data connectors (Azure Activity, Azure AD sign-in logs)
4. Explore the built-in hunting queries and analytics rules

Practice scenarios to complete:

• Detect a brute force attack from log data
• Identify data exfiltration through DNS query volume analysis
• Correlate a phishing email with subsequent malicious file execution
• Build a dashboard showing authentication trends over 30 days
• Create a custom correlation rule for detecting lateral movement

Use our Skills Assessment to benchmark your SIEM knowledge against the requirements for your target role.

Related Guides in This Series

• Network Security Fundamentals: Complete Guide
• Threat Intelligence: Skills, Tools, Career
• Zero Trust Security: What It Is and Why It Matters

Take the Next Step

Identify your skill gaps — Use our Skills Assessment to see where your SIEM and detection engineering abilities stand.
Build a learning plan — Visit the Career Coach to create a structured path to SIEM proficiency.

Frequently Asked Questions

Which SIEM is best for beginners?

Elastic Security (ELK Stack) is the most accessible for beginners because it is free to deploy with no ingestion limits. The documentation is extensive, and the community is active. However, if your goal is job readiness, Splunk Free (500MB/day limit) teaches the most marketable query language. Start with whichever you can set up and practice with consistently.

Do I need SIEM certification to get a SOC analyst job?

SIEM certifications are not strictly required but provide a measurable advantage. Splunk Core Certified User is the most recognized SIEM certification in job postings. It validates that you can search data, create reports, and use dashboards — exactly what a Tier 1 SOC analyst does daily. The certification costs around $130 and can be earned in two to four weeks of study.

How long does it take to learn a SIEM platform?

Basic proficiency (searching, filtering, reading alerts) takes two to four weeks of daily practice. Intermediate proficiency (writing correlation rules, building dashboards, onboarding log sources) takes two to three months. Advanced proficiency (performance tuning, custom app development, architecture design) takes six to twelve months of production experience. Start with the basics and build progressively.

— HADESS Team consists of cybersecurity practitioners, hiring managers, and career strategists who have collectively spent 50+ years in the field.