The best practice for the acceptable use of information assets is to ensure they are used for their intended business purpose. An Acceptable Use Policy (AUP), a key component of an Information Security Management System (ISMS) under ISO 27001, establishes rules to protect assets from misuse. Limiting the use of information and communication systems to business purposes minimizes risks such as malware infections from non-business websites, legal liability from inappropriate content, and loss of productivity. While some organizations may permit limited personal use, the foundational principle and most secure posture is that company assets are provided for business use only.

B. Interfering with or denying service to any user is a malicious act, a direct violation of any AUP, and often illegal. It is the opposite of acceptable use.

C. Playing computer games during office hours is a misuse of company time and resources and is typically explicitly forbidden in an AUP.

D. This statement is ambiguous but implies unauthorized access to network transmissions (e.g., sniffing), which is a serious security breach and a prohibited activity.

1. ISO/IEC 27002:2022, Information security, cybersecurity and privacy protection — Information security controls, Section 5.10 - Acceptable use of information and other associated assets. The implementation guidance for this control states that rules for acceptable use should be defined. A primary rule is to specify the authorized business purposes for which assets can be used, thereby restricting non-business activities that introduce risk.

2. von Solms, R., & von Solms, B. (2018). Cybersecurity and Information Security: What Everyone Needs to Know. Oxford University Press. In discussions on information security policies (Chapter 4), the authors emphasize that an AUP's core function is to "define what users are allowed and not allowed to do with the organization's IT assets," with the primary allowed function being job-related tasks.

3. Massachusetts Institute of Technology (MIT). (2023). Policy on the Use of MIT Information Technology Resources (Policy 13.2). This university policy, reflecting best practices, states: "The primary purpose of MIT's IT resources is to enhance and support the educational mission of the Institute... Uses that are inconsistent with this purpose are not permitted." This aligns directly with the principle of restricting use to the organization's primary (business) purpose.