What type of attack is indicated by the log entry with the string ../../../etc/passwd?

The log entry containing the string ../../../etc/passwd is characteristic of a directory traversal attack. This type of attack exploits vulnerabilities in a web application that improperly restricts access to files and directories. The attacker uses traversal sequences, such as "../", to navigate up the directory structure and access sensitive files that should be protected from direct access.

In this case, the reference to "/etc/passwd" is significant because this file in UNIX and Linux systems contains sensitive information about user accounts. If an attacker can successfully access this file by manipulating the file path, they can gain critical insights into the system's users and their hashed passwords, potentially leading to further attacks.

Understanding this context explains why directory traversal is the correct classification here, as it specifically pertains to unauthorized access attempts to restricted directories and files using path manipulation techniques.