Barney is a cybersecurity analyst who is attempting to configure network devices to prevent any potential malware from broadcasting outside the organization's network to an Internet command-and-control server. When he first analyzes a potential piece of malware, he sees that it is configured to send messages to a specific domain, which he promptly blocks. Several weeks later, he detects that same piece of malware on the network, as well as network traffic that indicates it is messaging a malicious server on the Internet. Which the following techniques did the malware most likely used to achieve this?