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Module 3 continuation of computer forensic
- 1. Module 3
- 2. Securing a Digital Incident or Crime Scene When investigating a digital incident or crime scene, securing the environment is critical to preserving evidence, maintaining its integrity, and ensuring proper chain of custody. Below are the key steps and best practices to follow:
- 3. 1. Initial Assessment Identify the Incident: Understand the nature of the digital crime or incident. Is it a data breach, unauthorized access, malware attack, or insider threat? Preserve Volatile Data: Certain data (like information in RAM, network traffic, or running processes) can be lost quickly. Use specialized tools to capture this information before shutting down systems. Document the Scene: Take detailed notes, photographs, and screenshots of what you observe in real-time. Record system states, open programs, and logged-in users. 2. Isolate the Affected Systems Prevent Further Damage: Disconnect affected systems from the network to prevent data exfiltration, remote access, or malware spreading. However, avoid turning off devices unless absolutely necessary, as valuable evidence may be lost. Secure Physical Access: Ensure that only authorized personnel can access the crime scene. Lock down rooms, servers, or computers involved in the incident.
- 4. 3. Maintain Chain of Custody Document Everything: Every interaction with the digital evidence must be thoroughly documented, including who accessed the systems, what actions were taken, and when. Use Tamper-Evident Methods: Seal and tag storage media (e.g., hard drives, USBs) and log their transfers to maintain the integrity of the evidence. Custody Logs: Keep a log of who has handled the evidence from the time of discovery to its presentation in court, ensuring that it has been properly secured and is unaltered. 4. Preserve Evidence Forensic Imaging: Create exact copies (forensic images) of storage devices to analyze them while keeping the original evidence intact. Use write-blocking devices to ensure that no changes are made to the original media. Verify the integrity of forensic images using cryptographic hashes (e.g., MD5, SHA256). Data Types: Preserve all types of evidence, including logs, emails, IP addresses, user credentials, encrypted files, network traffic, and system configuration data. Document Metadata: Note timestamps, file permissions, and access details to avoid tampering or deletion concerns.
- 5. 5.Protecting Network Evidence Network Logs: Capture network logs (e.g., firewall, router, VPN) as soon as possible to understand traffic patterns and potential external connections during the incident. Traffic Analysis: Use packet sniffers or intrusion detection systems (IDS) to capture and analyze live network traffic for suspicious behavior, such as exfiltration attempts or malware communication. 6. Securing Cloud-Based Evidence Collaborate with Cloud Providers: Work with cloud service providers to capture logs, access records, and other cloud-based evidence. Understand that cloud data can be volatile and may require legal action (e.g., subpoenas) for retrieval. Audit Logs: Retrieve audit logs from the cloud environment showing user activities, such as logins, file access, or modifications. Snapshots and Backups: Secure cloud snapshots and backups as potential sources of evidence.
- 6. 7. Ensure Legal Compliance Privacy Laws: Ensure compliance with local laws and regulations, such as GDPR, HIPAA, or CCPA, when handling digital evidence containing personal information. Warrants and Permissions: Obtain proper legal authorization (e.g., search warrants) when accessing sensitive or personal data. Unauthorized access could lead to evidence being inadmissible in court. Third-Party Involvement: If third parties, such as contractors or employees of service providers, are involved, their actions should also be documented and justified. 8. Collaboration with Law Enforcement and Forensics Experts Involve Forensic Experts: Digital forensics experts should be called in to handle evidence properly, analyze systems, and produce reports that will hold up in court. Coordinate with Law Enforcement: If the incident is a criminal matter, law enforcement agencies need to be contacted. Ensure smooth coordination by following proper procedures and maintaining a clear chain of custody.
- 7. 9. Post-Incident Analysis and Reporting Post-Incident Documentation: After securing evidence, provide a thorough report that includes: Timeline of the incident. Methods used to secure and collect evidence. Analysis of the compromised systems and suspected causes. Lessons Learned: Document and communicate the findings to improve the organizations security posture and reduce the likelihood of future incidents. Forensic Tools Used: Clearly document the forensic tools (e.g., EnCase, FTK, Wireshark) used during the investigation to establish the authenticity of the findings. 10. Final Considerations Avoid Contamination: Be cautious when interacting with digital evidence. Any alterations can compromise its admissibility in court. Use Authorized Tools: Only use certified forensic tools that are accepted by courts and industry standards to collect and analyze data.
- 9. Obtaining digital hash Obtaining a digital hash is an essential process in digital forensics, ensuring the integrity and authenticity of digital evidence. A digital hash is a cryptographic value generated from a file, drive, or set of data that uniquely identifies its contents. This value serves as a "digital fingerprint," making it possible to verify that the data has not been altered. Heres how you can obtain a digital hash: Steps for Obtaining a Digital Hash 1.Select a Hashing Algorithm The choice of the hashing algorithm is crucial. Common algorithms include: MD5 (Message Digest Algorithm 5): Produces a 128-bit hash value. It is fast but vulnerable to collision attacks (where two different files produce the same hash). SHA-1 (Secure Hash Algorithm 1): Generates a 160-bit hash. Stronger than MD5 but still susceptible to certain attacks. SHA-256: Part of the SHA-2 family, it generates a 256-bit hash value and is highly secure, making it widely recommended for forensic purposes.
- 10. 2. Prepare the Environment Ensure that your forensic workstation or tool is ready for hashing. When obtaining a hash from a physical storage device (like a hard drive), its critical to use a write-blocker to prevent any changes to the original data. Isolation: Make sure the evidence is disconnected from networks or external influences to avoid unintentional modifications. 3. Select the Appropriate Tool You can use various tools to generate a hash: Forensic Tools: FTK Imager: A powerful tool for creating forensic images and generating hashes. EnCase: A well-known commercial tool used for forensic imaging and analysis. Autopsy: An open-source digital forensics tool that supports hashing and other analysis features. Command-Line Utilities: Linux/Unix: Use md5sum, sha1sum, or sha256sum to generate the hash of a file or device. Windows: Use certutil or PowerShell cmdlets such as Get-FileHash.
- 11. 4. Obtain the Hash Hashing a File: Using FTK Imager: 1. Open FTK Imager and load the file or drive to be hashed. 2. Right-click on the file or drive and choose "Create Disk Image." 3. FTK Imager will calculate the hash value (MD5 and SHA-1 are usually calculated by default). 4. Document the hash values provided. Using Command Line: Open the terminal or command prompt and run the appropriate command: For MD5: md5sum /path/to/file For SHA-1: sha1sum /path/to/file For SHA-256: sha256sum /path/to/file The output will display the hash value followed by the file name. Hashing a Hard Drive: Using FTK Imager: 1. Select the entire hard drive or partition as the source. 2. Choose "Create Image" and specify the destination where you want the image saved. 3. FTK Imager will calculate the hash for the entire drive and display the values (MD5, SHA-1, or SHA-256). Using Command Line: For Linux-based systems, you can generate a hash for the entire drive: sha256sum /dev/sdX Replace /dev/sdX with the appropriate device identifier.
- 12. 5. Document the Hash Record Hash Values: Make sure to write down the hash values generated by the tool, including the algorithm used (MD5, SHA-1, or SHA-256). Additional Information: File or drive name. Date and time the hash was created. Tool or software used to generate the hash. Operating system and version used in the process. 6. Verify the Hash Verification: After copying or imaging the file or drive, generate a new hash of the copied data and compare it to the original hash value. Consistency Check: If the two hash values match, it means that the data is intact and has not been altered.
- 13. 7. Store the Hash Securely Store the hash values in a secure place, such as a digital evidence log or chain-of- custody document. This ensures that the integrity of the data can be verified at any point in the investigation. 8. Using Hashes in Legal and Investigative Contexts Present the hash as part of the forensic report, demonstrating that the evidence has remained unchanged since it was collected. Hash values can also be used to identify duplicate files, detect malware, and verify file integrity across different systems