Trusted Platform Module File Signing for Malware Forensics
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Solution Overview
Problem
Enterprise systems face challenges in determining the source and spread of threats within their networks due to the difficulty in obtaining verifiable forensic evidence, as users often deny involvement or attempt to avoid blame, making it hard for administrators to trace the origin and path of malware attacks.
Innovation Solution
Implementing a whitelisting solution that uses chained embedded signatures on files, managed through Trusted Platform Modules (TPMs), which creates a tamper-proof record of a file's movement across devices, allowing administrators to track the spread of malicious files and provide non-repudiable forensic evidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional forensic methods are used to trace malware spread, then administrators can attempt to identify the source, but users may deny involvement making the evidence unreliable
Solution Approach 1:
The system performs preliminary actions by embedding signed certificates and creating tamper-proof logs before any malware infection occurs. The TPM generates cryptographic keys and signs files at their creation point, establishing a trusted baseline that cannot be retroactively altered, thus preventing user denial by having evidence already in place
Solution Approach 2:
The TPM acts as an intermediary between the file system and the forensic analysis system. It provides cryptographic verification mechanisms that mediate between user claims and actual file origins, using digital signatures to objectively verify file provenance without requiring user testimony
2Loss of information
If administrators manually trace malware spread through user interviews and system checks, then they can gather information, but the process is time-consuming and lacks verifiable evidence
Solution Approach 1:
The system implements continuous feedback by automatically logging file operations, certificate chains, and system state changes in real-time. This creates an ongoing record of file movements and modifications that provides immediate information about malware spread without requiring manual investigation
Solution Approach 2:
The system creates cryptographic copies of file metadata and certificate information that can be independently verified. These copies serve as portable evidence that can be analyzed without accessing the original system, enabling rapid forensic analysis while preserving the integrity of the source system
3Measurement precision
If the system tracks file movement across devices, then it can identify the spread path, but implementing comprehensive tracking increases system complexity
Solution Approach 1:
The system merges file signing and tracking functions into the TPM's existing cryptographic operations. By combining malware detection, file signing, and movement tracking into a unified TPM-based mechanism, the system achieves comprehensive monitoring without adding separate complex tracking infrastructure
Solution Approach 2:
The TPM serves multiple functions: it generates cryptographic keys, signs files, verifies certificates, and logs system events. This multi-functionality allows the system to achieve precise tracking using a single component rather than requiring separate specialized systems for each function
4Ease of operation
If the system requires user cooperation to identify malware entry points, then it can gather testimonial evidence, but users may refuse to cooperate or provide false information
Solution Approach 1:
The system performs self-verification by automatically analyzing certificate chains and cryptographic signatures to identify malware entry points without requiring user input. The TPM independently verifies file origins through cryptographic proof, making the system self-sufficient and eliminating dependence on user cooperation
Data Source
AI summary
Managed devices containing a Trusted Platform Module (TPM) to provide a trusted environment generate a device certificate at initialization of the TPM and send the device certificate to a management console for storing in a certificate database. Upon detecting a file of interest, the TPM signs the file, adding to a signature list created by previous managed devices. The signature list can be used to analyze the spread of the file across the system of managed devices, including tracking the file to the first managed device to have had a copy, without requiring real-time access to the managed devices during the spread of the file. In some embodiments, additional security measures may be taken responsive to determining the first managed device and the path the file has taken across the system of managed devices.