Explanation
Using digital evidence to provide validation that an attack has actually occurred is an example of computer forensics. This is because computer forensics is a discipline that involves the identification, preservation, analysis, and presentation of digital evidence from various sources, such as computers, networks, mobile devices, etc., to support investigations of cyber incidents or crimes. Computer forensics helps to provide validation that an attack has actually occurred, by examining the digital traces or artifacts left by the attackers on the compromised systems or devices, and by reconstructing the sequence and timeline of events that led to the attack. The other options are not examples of using digital evidence to provide validation that an attack has actually occurred, but rather different techniques or processes that are related to computer forensics, such as extraction (B), identification C, or data acquisition (D).

Explanation
Trend/variance-detection tools are tools that look for anomalies in user behavior. These tools use statistical methods to establish a baseline of normal user activity and then compare it with current or historical data to identify deviations or outliers. These tools can help to detect unauthorized access, fraud, insider threats, or other malicious activities.

The GREATEST advantage of using a virtual private network (VPN) over dedicated circuits and dial-in servers is that it is more cost effective. This is because a VPN is a technology that creates a secure and encrypted connection between a client and a server over an existing public network, such as the Internet. A VPN reduces the cost of establishing and maintaining a secure communication channel, as it does not require any additional hardware, software, or infrastructure, unlike dedicated circuits and dial-in servers, which require dedicated lines, modems, routers, switches, etc. The other options are not the greatest advantage of using a VPN over dedicated circuits and dial-in servers, because they either involve security (A), reliability (B), or speed C aspects that may not be significantly different or better than dedicated circuits and dial-in servers.

The MOST important thing to verify when reviewing the effectiveness of an organization's identity management program is whether the processes are aligned with industry best practices. Identity management is the process of managing the identities and access rights of users across an organization's systems and resources. Industry best practices provide guidelines and standards for how to implement identity management in a secure, efficient, and compliant manner.