Fenrir Simple Bash IOC Scanner

Fenrir is a bash script-based IOC (Indicators of Compromise) scanner designed for Linux, Unix, and macOS systems. The tool performs scanning operations without requiring installation or agent deployment, utilizing common system utilities to extract and analyze file attributes. The scanner supports multiple IOC detection methods including hash-based detection for MD5, SHA1, and SHA256 values using standard system tools like md5sum, sha1sum, and sha commands. It performs filename matching by checking for substring matches within full file paths and conducts string-based searches using grep to identify suspicious content within files. Fenrir includes C2 server detection capabilities by analyzing output from lsof commands to identify potential command and control communications. The tool features a Hot Time Frame function that uses stat commands to identify files created within specified epoch timestamp ranges. The scanner implements smart exclusions based on file size, extensions, and directory paths to optimize scan performance and reduce processing time. It operates with a low system footprint and can be deployed using Ansible playbooks with RAM drive solutions for enhanced performance. The tool is positioned as the third iteration in a series that includes THOR (commercial APT scanner) and LOKI (YARA-based IOC scanner), designed to address limitations found in its predecessors while maintaining simplicity and broad system compatibility.