What is an attack surface as compared to a vulnerability?

An analyst is investigating a host in the network that appears to be communicating to a command and control server on the Internet. After collecting this packet capture the analyst cannot determine the technique and payload used for the communication.
Which obfuscation technique is the attacker using?

Refer to the exhibit.

This request was sent to a web application server driven by a database. Which type of web server attack is represented?

Refer to the exhibit.

Which packet contains a file that is extractable within Wireshark?

Refer to the exhibit. What is the potential threat identified in this Stealthwatch dashboard?