Detecting Malicious Email Forwarding Rules Attack

v20260601

detecting-email-forwarding-rules-attack

This guide provides a comprehensive methodology and technical approach for detecting malicious email forwarding rules. It is crucial for threat hunting, incident response, and proactive security assessments to identify persistent access mechanisms used by adversaries for intelligence collection and Business Email Compromise (BEC) attacks. It outlines necessary prerequisites, workflow steps, and key threat indicators (T1114).

Cybersecurity Threat Hunting Email BEC T1114 Persistence

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Overview

Detecting Email Forwarding Rules Attack

When to Use

When proactively hunting for indicators of detecting email forwarding rules attack in the environment
After threat intelligence indicates active campaigns using these techniques
During incident response to scope compromise related to these techniques
When EDR or SIEM alerts trigger on related indicators
During periodic security assessments and purple team exercises

Prerequisites

EDR platform with process and network telemetry (CrowdStrike, MDE, SentinelOne)
SIEM with relevant log data ingested (Splunk, Elastic, Sentinel)
Sysmon deployed with comprehensive configuration
Windows Security Event Log forwarding enabled
Threat intelligence feeds for IOC correlation

Workflow

Formulate Hypothesis: Define a testable hypothesis based on threat intelligence or ATT&CK gap analysis.
Identify Data Sources: Determine which logs and telemetry are needed to validate or refute the hypothesis.
Execute Queries: Run detection queries against SIEM and EDR platforms to collect relevant events.
Analyze Results: Examine query results for anomalies, correlating across multiple data sources.
Validate Findings: Distinguish true positives from false positives through contextual analysis.
Correlate Activity: Link findings to broader attack chains and threat actor TTPs.
Document and Report: Record findings, update detection rules, and recommend response actions.

Key Concepts

Concept	Description
T1114.003	Email Forwarding Rule
T1114.002	Remote Email Collection
T1098.002	Additional Email Delegate Permissions

Tools & Systems

Tool	Purpose
CrowdStrike Falcon	EDR telemetry and threat detection
Microsoft Defender for Endpoint	Advanced hunting with KQL
Splunk Enterprise	SIEM log analysis with SPL queries
Elastic Security	Detection rules and investigation timeline
Sysmon	Detailed Windows event monitoring
Velociraptor	Endpoint artifact collection and hunting
Sigma Rules	Cross-platform detection rule format

Common Scenarios

Scenario 1: BEC actor creating forwarding rule to external email
Scenario 2: Compromised account with rule deleting security alerts
Scenario 3: Inbox rule forwarding CEO emails to attacker mailbox
Scenario 4: OAuth app abuse creating transport rules for data collection

Output Format

Hunt ID: TH-DETECT-[DATE]-[SEQ]
Technique: T1114.003
Host: [Hostname]
User: [Account context]
Evidence: [Log entries, process trees, network data]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]
Recommended Action: [Containment, investigation, monitoring]

Info

Category Development

Name detecting-email-forwarding-rules-attack

Version v20260601

Size 14.65KB

Source mukul975/Anthropic-Cybersecurity-Skills

Updated At 2026-06-03