Anonymity services reduce the amount of information available that can be used to track an adversary's activities. Multiple options are available to hide activity, limit tracking, and increase anonymity.12
Difficulty for the Adversary
Easy for the Adversary (Yes/No): Yes
Explanation: Easy access to anonymizers, quasi-anonymous services like remailers, TOR, relays, burner phones, etc.
Detectable by Common Defenses (Yes/No/Partial): No
Explanation: Depends on service. Some are easy to detect, but are hard to trace (e.g., TOR).