Final answer:
A network sniffer is the tool that can be used to identify the IP address of a coworker by monitoring network traffic in real time.
Step-by-step explanation:
A user on a network who is planning to launch an exploit against a coworker and needs to identify the IP address of a coworker in a particular department would likely use a network sniffer. This tool allows the user to watch network traffic in real-time and could be used to identify a target's IP address based on the traffic originating from or directed to the coworker's device. It should be noted, however, that using a sniffer or any other method to intercept or monitor network traffic without authorized permissions can be considered illegal and unethical, and can lead to legal consequences and violations of privacy.