Shoulder surfing is primarily concerned with observing what type of information?

Shoulder surfing is primarily focused on the act of observing sensitive information, particularly logon credentials and financial details, by looking over someone's shoulder while they are entering this information. This practice exploits the physical aspect of security, where an attacker might position themselves close enough to view someone's screen or keyboard without the victim's awareness.

Logon credentials, such as usernames and passwords, are crucial to system security, and their compromise can lead to unauthorized access to personal accounts or sensitive data. Financial information, including credit card numbers and bank account details, is equally sensitive, and if obtained, can result in financial theft or fraud.

In contrast, the other options do not align with the concept of shoulder surfing. Software installation procedures, network configurations, and physical security measures typically do not require direct observation in the same immediate and vulnerable manner that logon credentials and financial information do. These other types of information tend to involve more layered security measures and are less likely to be exposed through casual observation.