Email Sequence Detection for Multi-Segment Malicious Attacks

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Solution Overview

Problem

Existing email security systems struggle to efficiently detect multi-stage malicious email attacks, such as BEC spam attacks, which are challenging due to the computational complexity of existing detection methods and the rapid evolution of attack techniques, leading to potential financial and information losses.

Innovation Solution

An email security system that stores previously determined maliciousness predictions for past emails in a record database, allowing for efficient retrieval and combination with incoming email predictions to determine an overall maliciousness verdict, thereby reducing the need for real-time complex computations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing detection methods are used to identify multi-stage malicious email attacks, then detection accuracy can be maintained, but computational complexity increases and real-time detection efficiency decreases

Engineering Contradiction:
Improvedetection accuracyVSAvoidcomputational complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The detection system segments the email analysis process into multiple independent stages: initial feature extraction, preliminary maliciousness assessment, sequential email pattern recognition, and final verdict determination. Each stage processes specific features independently, reducing overall computational complexity while maintaining comprehensive detection accuracy for multi-stage attacks

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system performs preliminary analysis by extracting key features and determining initial maliciousness predictions for each email before full sequence analysis. This preliminary action prepares data in advance, enabling faster real-time processing of multi-stage attack patterns without sacrificing detection accuracy

Inventive Principle:
Principle #10Preliminary action

2Reliability

If comprehensive analysis of multiple emails is performed in real-time, then detection of multi-stage attacks improves, but processing time increases

Engineering Contradiction:
Improvedetection effectivenessVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The system extracts email features and determines preliminary maliciousness predictions before complete sequence analysis is performed. This advance preparation of data enables rapid real-time processing when multi-stage attack patterns are identified, reducing processing time while maintaining comprehensive detection effectiveness

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The detection system operates in periodic cycles: initial feature extraction for incoming emails, sequential analysis when patterns are detected, and verdict determination. This periodic operation allows the system to maintain real-time responsiveness for most emails while performing comprehensive multi-stage analysis only when necessary

Inventive Principle:
Principle #19Periodic action

3Productivity

If traditional email security scanning is used, then individual malicious emails can be blocked, but multi-stage attack sequences are missed

Engineering Contradiction:
Improveemail processing speedVSAvoidattack detection completeness
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The system performs multiple functions simultaneously: it processes individual emails for immediate delivery decisions while also analyzing sequences of emails from the same sender to identify multi-stage attack patterns. This multi-functionality enables the system to maintain high email processing speed while achieving complete attack detection through sequential pattern recognition

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentUS12603905B2Detecting multi-segment malicious email attacks
Publication Date: 2026.04.14 CISCO TECHNOLOGY INC
  • US12603905B2 patent drawing
  • US12603905B2 patent drawing
  • US12603905B2 patent drawing

AI summary

A method to perform the techniques described herein includes receiving a first email from a first sender to a first receiver. The method may include determining a first maliciousness prediction that indicates a first likelihood that the first email is malicious. The method may include determining that the first maliciousness prediction fails to satisfy a maliciousness pattern associated with malicious emails. The method may include receiving a second email from the first sender to the first receiver. The method may include determining that the first email and second email were received within a threshold period of time. The method may include determining an overall maliciousness prediction that indicates an overall likelihood that the first email and second email in combination are malicious. The method may include determining that the overall maliciousness prediction satisfies the maliciousness pattern.