The Micro-Temporal Metadata Audit
When executing an active security incident response on an Ubuntu Linux server, tracking structural changes to the filesystem in real-time is critical. If an attacker is currently actively modifying file permissions (e.g., using chmod) or changing file ownership (e.g., using chown), simply checking when the file was last accessed (-amin) or when the text inside the file was modified (-mmin) is insufficient. You must explicitly audit the file’s Change Time (ctime) at a minute-level granularity to track exact modifications to the inode metadata.
Using the find Command with -cmin
The Linux find command utilizes the -cmin flag to explicitly search for files based on the exact number of minutes that have elapsed since their metadata was last altered.
- Open your Terminal application (Ctrl + Alt + T) or log into your server via SSH.
- To scan the
/etc/directory for any system configuration files whose permissions or ownership were changed exactly 15 minutes ago, type the following command exactly: sudo find /etc/ -type f -cmin 15- Press Enter.
Exact Minute Precision
By omitting the + or - mathematical operators, the command engine is instructed to perform a strict equality check. The search will completely ignore files whose metadata changed 14 minutes ago or 16 minutes ago; it strictly returns files that experienced a metadata modification exactly 15 minutes ago. This command is an absolute necessity for security administrators attempting to isolate and verify the exact structural changes executed by an automated script or a malicious actor during a very specific operational window.