Final answer:
The code portion of a rootkit responsible for initiating the installation process, often triggered by malicious links or infected files, is known as a dropper.
Step-by-step explanation:
The code portion of a rootkit that gets the installation started and can often be activated by clicking on a link to a malicious website in an email or opening an infected .pdf file is known as a dropper. A dropper is a small program that is designed to install malware (such as a rootkit) onto a target system. It acts as a vehicle for the rootkit, allowing it to be discreetly installed without the user's knowledge.The dropper code portion of a rootkit is responsible for getting the rootkit installation started. It can be activated by clicking on a link to a malicious website in an email or by opening an infected .pdf file. Once the dropper is activated, it allows the rootkit to be installed on the system.