The ID Spectre refers to the specialist:
Next to nothing is known about the presumed wet-works Specialist, Spectre.
The designation itself is a codename agreed upon by the various agencies that have pooled their intelligence on unsolved assassinations, inferring his or her existence based on either evidence found at the scene or from fragmentary reports given by shaken bystanders.
Despite heavy redaction, all accounts suggest an individual capable of extraordinary stealth, able to evade or neutralize the most sophisticated of manned or automated security set-ups.
In every case, Spectre's victims have been slain with surgically precise mid-line stab wounds with rarely any sings of struggle.
- Spectre (Specialist) - callofduty.fandom.com