Fnord

Fnord is a pattern extraction tool designed for analyzing obfuscated code and malware samples. The tool processes files using a sliding window approach to extract byte sequences of varying lengths and generates statistical analysis of the most frequently occurring patterns. The tool creates detailed tables showing sequence information including length, occurrence frequency, actual byte sequences, and entropy calculations. This statistical approach helps analysts identify significant patterns within obfuscated or packed malware samples. Fnord includes experimental YARA rule generation capabilities that calculate scores based on sequence length and occurrence frequency. The tool processes each identified sequence to detect potentially interesting patterns using a predefined keyword list and applies Levenshtein distance calculations to filter out irrelevant or common sequences. The pattern extraction methodology focuses on identifying meaningful byte sequences that could represent important code structures, API calls, or other significant elements within obfuscated malware samples. This approach assists malware analysts in understanding code structure and behavior even when traditional static analysis methods are hindered by obfuscation techniques.