The Malware Hunt
In Ubuntu Linux, files do not rely on extensions like .exe or .bat to run. Instead, a file can only be executed as a program if its metadata specifically contains an “execute” permission bit. If you are auditing a compromised web server—especially an upload directory like /var/www/uploads/ where users are only supposed to upload static images—finding a hidden file with execute permissions is a massive red flag. It usually indicates a hacker has uploaded a backdoor script. To secure the server, you must explicitly scan for runnable files.
Using the find Command with -executable
The Linux find command utilizes the -executable flag to search for files that the current user has the explicit permission to run as a program.
- Open your Terminal application (Ctrl + Alt + T) or log into your server via SSH.
- To search the
/var/www/uploads/directory for any hidden scripts or binaries, type the following command exactly: find /var/www/uploads/ -type f -executable- Press Enter.
Permission-Based Filtering
The -executable flag evaluates the actual POSIX permission matrix (read, write, execute) rather than looking at file names or content. We combine it with -type f to ensure the search engine only returns normal files (otherwise, it would return every single directory, as directories must be “executable” to enter them). This command allows administrators to instantly isolate dangerous scripts hidden inside innocent-looking folders, making it an absolutely critical tool for rapid cybersecurity incident response.