How to Find SetUID Files in Ubuntu Linux (Security Audit)

The Privilege Escalation Threat

In Ubuntu Linux, files can be assigned a special permission flag known as “SetUID” (SUID). When a standard, unprivileged user executes a program with the SUID flag, the program temporarily assumes the security privileges of the file’s owner—which is almost always the “root” administrator. While this is necessary for critical commands like passwd (allowing normal users to change their own passwords), it is a massive security risk if applied incorrectly. If an attacker finds a vulnerable SUID script on your server, they can exploit it to instantly gain full root access. System administrators must routinely audit their servers for unauthorized SUID files.

Using the find Command with -perm

The Linux find command utilizes the -perm flag combined with the specific octal permission code (4000) to isolate files with the SUID bit enabled.

1. Open your Terminal application (Ctrl + Alt + T) or log into your server via SSH.
2. To search the entire root filesystem (/) for any file possessing SUID permissions, type the following command exactly:
3. sudo find / -type f -perm -4000 2>/dev/null
4. Press Enter and provide your administrator password.

Suppressing Errors

Because you are starting the search at the absolute root of the hard drive (/), the find command will inevitably attempt to scan specialized virtual directories (like /proc) where even the root user is denied permission, resulting in hundreds of “Permission denied” errors flooding your screen. Appending 2>/dev/null to the end of the command is critical. It forces the terminal to completely swallow and hide all error messages, ensuring your screen only displays the clean, actionable list of SUID files you need to audit.