The best permission that the developer should assign to the log file to ensure requirements are met is append. A log file is a type of file that records and stores the information or the data about the activities, events, or issues that occur on a system or a network, or on a software application, such as the user activity. A log file can provide various benefits, such as monitoring, auditing, reporting, or troubleshooting the system, the network, or the software application. A permission is a type of access right or privilege that grants or denies the user or the role the ability to perform certain actions or tasks on a system or a network, or on a file or a folder, such as the log file. A permission can be classified into four types, which are:

Read: The user or the role can view or read the content or the information of the file or the folder.

Write: The user or the role can modify or overwrite the content or the information of the file or the folder.

Execute: The user or the role can run or execute the file or the folder, if it is an executable file or a folder.

Append: The user or the role can add or append new content or information to the end of the file or the folder, but cannot modify or overwrite the existing content or information of the file or the folder. Append is the best permission that the developer should assign to the log file to ensure requirements are met, as it can provide the user or the role with the necessary and sufficient access right or privilege to create and store the log entries or records of the user activity, without compromising the security or the integrity of the log file . References: [CISSP CBK, Fifth Edition, Chapter 6, page 581]; [100 CISSP Questions, Answers and Explanations, Question 14].