One of the risks of using legacy software is the lack of vendor support. This means that the vendor may no longer provide security patches, software updates, or technical support for the software. This leaves the software vulnerable to new security threats and vulnerabilities that could be exploited by attackers.

A jump server is a secure host that allows users to access other servers within a network. The jump server acts as an intermediary, and users can access other servers via the jump server after authenticating with MFA.

Syslogs are log files that are generated by devices on the network and contain information about network activity, including user logins, device connections, and other events. By analyzing these logs, the IT security team can identify the source of the threatening voicemail messages and take the necessary steps to address the issue

PKI is a security technology that enables secure communication between two parties by using cryptographic functions. It consists of a set of components that are used to create, manage, distribute, store, and revoke digital certificates. PKI provides a secure way to exchange data between two parties, as well as a trust provider to ensure that the data is not tampered with. It also helps to create a highly scalable solution, as the same certificate can be used for multiple parties.
According to the CompTIA Security+ Study Guide, "PKI is a technology used to secure communications between two external parties. PKI is based on the concept of digital certificates, which are used to authenticate the sender and recipient of a message. PKI provides a trust provider to ensure that the digital certificate is valid and has not been tampered with. It also provides a scalable solution, as multiple parties can use the same certificate."

According to NIST Special Publication 1800-4B1, some of the security controls that can be used to protect mobile devices include:
Root and jailbreak detection: ensures that the security architecture for a mobile device has not been compromised.
Encryption: protects the data stored on the device and in transit from unauthorized access.
Authentication: verifies the identity of the user and the device before granting access to enterprise resources.
Remote wipe: allows the organization to erase the data on the device in case of loss or theft.
Screen lock timer: sets a time limit for the device to lock itself after a period of inactivity.