Centralized Binary Logging is a feature specific to Microsoft Internet Information Services (IIS) 6.0, designed for web farm environments. It enables multiple websites to write their log data to a single, central file in a binary, unformatted manner. This process is more efficient than writing individual text-based logs. The default file extension for these centralized binary log files is .ibl, which stands for Internet Binary Log. To analyze these logs, an investigator must use a specialized tool, such as Microsoft's Log Parser, to convert the binary data into a human-readable format.

A. .cbl: This is not the standard extension used by Microsoft IIS for its Centralized Binary Logging feature, despite the acronym's apparent relevance.
B. .log: This is a generic extension for log files, which are typically text-based. It does not specifically denote the binary format used by IIS Centralized Logging.
D. .txt: This extension is for plain text files. The question explicitly states the log data is "binary and unformatted," which is incompatible with the .txt format.

1. Microsoft Corporation. (2003). Centralized Binary Logging. Microsoft TechNet. In the documentation for IIS 6.0, it is stated: "Centralized binary logging allows multiple Web sites to write unformatted, binary log data to a single log file, which is named Iislog.ibl by default." (This content is widely archived from the original Microsoft TechNet library for IIS 6.0).

2. Stanek, W. R. (2006). Microsoft Windows Server 2003 Administrator's Pocket Consultant (2nd ed.). Microsoft Press. In Chapter 16, "Managing Web and FTP Sites," the section on logging configurations details the Centralized Binary Logging option and its use of .ibl files for high-performance logging in server farms.

3. Shinder, D. L., & Cross, M. (2008). Scene of the Cybercrime (2nd ed.). Syngress Publishing. In Chapter 11, "Investigating Network Traffic," the book discusses various web server log formats, identifying IIS 6.0's centralized binary logging feature and its use of the .ibl file extension (p. 368).