In regards to the article the OP links above, there are two things that stand out to me:
1) "Some scholars, including Stephen Hawking, are concerned that the deliberate sending of radio signals into deep space and the leakage radiation could be a serious risk, because we are revealing the location of our planet to hostile alien civilizations."
2) "There is absolutely no need to worry about this. The advanced civilizations from our Galaxy know that we exist and know exactly where we are. The spectral analysis of Earth’s atmosphere alone is enough to reveal us, because it is specific to planets with complex life and technological civilizations. We cannot hide our atmosphere."
My ponderings: Regarding the first quote from the article: Mr. Hawking is a very smart man. Everyone pretty much knows who he is, what he does and that he lives amongst us. We -know- Mr. Hawking. He makes a lot of sense and he has facts to back up his 'sense.'
Now regarding the second quote from the article: I would very much like to know -who- knows enough to be able to state in any shape or form that: 'The advanced civilizations from our Galaxy know we exist and know exactly where we are.'
This second quote is stated with a high sense of certainty, enough certainty to be almost down right impossible to actually clarify or to -know- as utter fact.
I think the word 'if' before that statement would have made it a little bit more 'believable', because we actually do not -know- anything.
(This post has not been intended to flame or to demonstrate a verbal injustice to the OP. This has been clearly a criticism of the the article itself. )
My words of advice: Listen to Mr. Hawking.
Kind Regards.