It is currently impossible to guarantee that a signal received from space would not be a form of deception or "spoofing." The vast distances and technical barriers to interstellar communication make it inherently challenging to verify the authenticity and intent behind such a signal.

Even if a signal's characteristics appear similar to what might be theoretically expected from an advanced civilization, confirming its legitimacy would require corroborating evidence. Establishing two-way communication, observing consistent patterns over time, and potentially verifying the signal through independent observations from separate locations could enhance confidence in its non-deceptive nature.

Ultimately, confirming beyond doubt that a purported message from extraterrestrial entities is genuine and free from tampering remains an open question in astronomy and would present a monumental scientific and intellectual milestone if ever achieved.