Final answer:
Yersinia is a network tool used for tests such as DHCP starvation attacks, which are illegal without proper authorization. When operating in DHCP mode, Yersinia typically uses the default source port 68, the standard client port for DHCP communications.
Step-by-step explanation:
The question is about using Yersinia, a network testing tool, specifically in its DHCP mode to conduct a DHCP starvation attack on a system using Parrot Security OS. In a DHCP starvation attack, an attacker exhausts the DHCP server's IP address pool by sending DHCP REQUEST messages with spoofed MAC addresses, which can lead to denial of service for legitimate network users trying to obtain an IP address.
The default source port used by Yersinia in DHCP mode is typically 68, which is the client port used in DHCP communications. The DHCP server listens on port 67, and when a client sends a DHCP discover packet to find a DHCP server, it uses source port 68. After a server responds to the client, subsequent DHCP messages, such as requests and acknowledgements, continue to use port 68 as the client's source port.
It is important to note that conducting a DHCP starvation attack is considered unlawful and unethical in real-world scenarios unless performed in a controlled environment for educational or testing purposes and with proper authorization.