Which of the following is an indication of unauthorized use of a standard user account?

The indication of unauthorized use of a standard user account is best represented by the use of a secret account. Secret accounts, often referred to as "backdoor" accounts, are not disclosed to system administrators and may be used by unauthorized individuals to gain access to systems without normal authentication processes. If a secret account is utilized within an environment where standard user accounts are expected to be in use, it raises significant security concerns regarding unauthorized access and potential breaches.

While alerts from network and host Intrusion Detection Systems (IDS) may signify suspicious activity, they are more general indicators of potential threats and can be triggered by various legitimate activities. Misplaced hardware parts may suggest physical security issues, but do not directly point to unauthorized account usage. An increase in resource usage is also not definitive, as it could stem from legitimate user activities or system processes, rather than an indication of unauthorized access through accounts. Thus, the presence of a secret account stands out as a clear sign of potential unauthorized use.