behavioral-detections

Behavioral Detection Engineering

Design and implement behavioral detection rules that identify attack patterns across multiple events using CrowdStrike NG-SIEM's correlate() function.

When to Use This Skill

Use this skill when you need to:

• Design attack chain detections (recon → escalation → persistence)
• Build behavioral rules that span multiple events over time
• Create compound detections from multiple rule triggers
• Correlate events across different data sources (AWS + EntraID + CrowdStrike)
• Detect multi-stage attacks that single-event rules would miss

Quick Start: Your First Behavioral Rule

// Detect failed logins followed by successful access
correlate(
  FailedLogins: {
    event.outcome="failure"
    event.action=/UserLogon|Sign-in/
  },
  SuccessfulLogin: {
    event.outcome="success"
    event.action=/UserLogon|Sign-in/
    | user.email <=> FailedLogins.user.email
  },
  sequence=true,
  within=30m,
  globalConstraints=[user.email]
)
| table([SuccessfulLogin.user.email, FailedLogins.source.ip])

Core Concepts

Behavioral vs Correlation Rules

Type	Function	Use Case
Correlation Rule	Single-event threshold	"Alert on 50+ failed logins"
Behavioral Rule	Multi-event pattern via correlate()	"Alert on failed logins FOLLOWED BY success"

correlate() Key Components

1. Named Queries: Each event pattern has a unique name

   QueryName: { filter_expression }
   

2. Link Operator <=>: Correlates fields between queries

   | user.email <=> OtherQuery.user.email
   

3. Sequence: Enforce chronological order

   sequence=true  // Events must occur in order
   

4. Time Window: Constrain event timing

   within=1h  // All events within 1 hour
   

5. Global Constraints: Fields all events must share

   globalConstraints=[user.email, cloud.account.id]
   

Attack Pattern Design Workflow

Step 1: Define the Attack Chain

Identify the stages of the attack you want to detect:

Stage	Event Type	Example
Reconnaissance	Read/List operations	DescribeInstances, ListBuckets
Initial Access	Authentication events	UserLogon, ConsoleLogin
Privilege Escalation	Permission changes	AttachUserPolicy, AddMemberToRole
Persistence	Credential creation	CreateAccessKey, CreateLoginProfile
Exfiltration	Data access	GetObject, FileDownloaded

Step 2: Map to correlate() Queries

correlate(
  // Stage 1: Reconnaissance
  Recon: {
    event.action=~in(values=["DescribeInstances", "ListBuckets"])
  },

  // Stage 2: Privilege Escalation
  PrivEsc: {
    event.action="AttachUserPolicy"
    | Vendor.userIdentity.arn <=> Recon.Vendor.userIdentity.arn
  },

  // Stage 3: Persistence
  Persist: {
    event.action="CreateAccessKey"
    | Vendor.userIdentity.arn <=> Recon.Vendor.userIdentity.arn
  },

  sequence=true,
  within=2h,
  globalConstraints=[Vendor.userIdentity.arn]
)

Step 3: Add Context and Output

| ipLocation(Recon.source.ip)
| case {
    Recon.source.ip.country!="United States" | _Risk := "Critical" ;
    * | _Risk := "High" ;
}
| table([_Risk, Recon.Vendor.userIdentity.arn, Recon.source.ip, Recon.source.ip.country])

Supporting Files

• attack-patterns.md - MITRE ATT&CK-aligned attack chain patterns
• aws-behavioral-rules.md - AWS-specific behavioral detection examples
• entraid-behavioral-rules.md - EntraID authentication pattern examples
• detection-chaining.md - How to correlate rule triggers (RTEs)

Detection Output Types

Outcome	Field Value	Description
Behavioral Detection	Ngsiem.event.outcome="behavioral-detection"	Multi-event correlate() rule
Correlation Detection	Ngsiem.event.outcome="correlation-rule-detection"	Single-event threshold rule
Behavioral Case	Ngsiem.event.outcome="behavioral-case"	Creates investigation case

Best Practices

1. Start Simple, Add Complexity

// Start with 2 events
correlate(
  EventA: { ... },
  EventB: { ... | field <=> EventA.field },
  within=1h
)

// Then add more stages after validation

2. Choose Appropriate Time Windows

Attack Pattern	Recommended within
Authentication brute force	15-30m
Privilege escalation chain	1-2h
Data staging → exfil	4-24h
Insider threat patterns	24-72h

3. Use globalConstraints for Shared Fields

// Cleaner than repeating links
globalConstraints=[user.email, cloud.account.id]

4. Sequence Only When Order Matters

// Attack chain - order matters
sequence=true

// Alert correlation - either can come first
sequence=false

5. Validate Lookback > Within

search:
  filter: |
    correlate(... within=2h ...)
  lookback: 4h  # Must exceed 'within' value

6. Validate Component Query Volume Before Wiring

Before assembling a correlate() rule, run each component query independently against 30d of data. A noisy component query produces a noisy behavioral rule — and behavioral rules are harder to tune after the fact because the correlate() wrapper obscures which leg is generating volume.

// Run each leg standalone first:
ngsiem_query: <component_filter_A> | groupBy([actor, key_field], function=count()) | sort(count, desc)
ngsiem_query: <component_filter_B> | groupBy([actor, key_field], function=count()) | sort(count, desc)

If any component returns unexpectedly high volume, tune it individually before combining. The target is that each leg fires only on genuinely anomalous events — a behavioral rule combining two noisy legs produces noisy² alerts.

Common Patterns

Pattern: Authentication Abuse

Failed attempts → Successful login See entraid-behavioral-rules.md

Pattern: Privilege Escalation Chain

Create user → Attach admin policy → Create credentials See aws-behavioral-rules.md

Pattern: Detection Correlation

Combine multiple rule triggers into compound alert See detection-chaining.md

Pattern: Cross-Source Correlation

Endpoint activity → Cloud API calls See attack-patterns.md

Syntax Reference

For complete correlate() syntax documentation, see:

• correlate-function.md in the logscale-security-queries skill

Need Help?

• Designing attack chains? → See attack-patterns.md
• AWS-specific patterns? → See aws-behavioral-rules.md
• EntraID patterns? → See entraid-behavioral-rules.md
• Chaining detections? → See detection-chaining.md
• CQL syntax issues? → See correlate-function.md