has used embedded image tags (known as web bugs) with unique per-recipient tracking links in their emails for the purpose of identifying which recipients opened messages.
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request. ### Instruction: List the MITRE techniques contained in the text. ### Input: has used embedded image tags (known as web bugs) with unique per-recipient tracking links in their emails for the purpose of identifying which recipients opened messages. ### Response: T1598.003.