In a digital forensics investigation, conclusions must be based on verifiable evidence, not speculation. The filenames Zer0.tar.gz and copy.tar.gz, while potentially suspicious, are not definitive indicators of any specific activity. File names can be arbitrarily chosen by any user, administrator, or application. Without further analysis of the files' contents, metadata (timestamps, ownership, permissions), location, and associated network or process activity, it is impossible to conclude whether they are part of a malicious attack, a legitimate backup, or simply operational files. The principle of due diligence in forensics requires treating such items as potential evidence requiring further investigation, not as proof of a specific event.

A. The system files have been copied by a remote attacker: This is a plausible scenario but cannot be concluded from filenames alone. A local user or administrator could have created these files for legitimate purposes.
B. The system administrator has created an incremental backup: While possible, backup archives are typically named more descriptively (e.g., including dates or hostnames). This is a guess, not a conclusion supported by the evidence provided.
C. The system has been compromised using a t0rnrootkit: This is incorrect. The well-documented t0rn rootkit package is typically named t0rn.tar.gz. The filenames provided do not match the known indicators of compromise (IOCs) for this specific rootkit.

1. National Institute of Standards and Technology (NIST) Special Publication 800-86, Guide to Integrating Forensic Techniques into Incident Response. Section 3.3, "Data Analysis," emphasizes that analysis involves "transforming the collected information so that it is suitable for drawing conclusions," which implies that raw data (like a filename) is not in itself a conclusion. The process requires correlation and examination, not assumption.

2. Spitzner, L. (2003). Know Your Enemy: The Tools and Methodologies of the Script-Kiddie. The Honeynet Project. This document, in its analysis of common attack tools from that era, details the standard installation and file artifacts of the t0rn rootkit. The files mentioned in the question are not listed as part of the standard t0rn kit distribution or installation footprint.

3. Carvey, H. (2005). The Windows Forensic Analysis DVD Toolkit. Syngress Publishing. While focused on Windows, the forensic principles are universal. Chapter 1, "Forensic Analysis," discusses the methodology of forming a hypothesis based on indicators and then seeking evidence to prove or disprove it, rather than jumping to a conclusion from a single indicator like a filename.