I don't think there's a great need to be too careful at all.
Firstly, we already know that intelligent and technological life is extremely rare. I am careful to make that distinction. There is lots of intelligent life on this planet, but only one intelligent, technological culture. We are no more intelligent than any other humans in the past, but we've only had the technology to detect or signal extra terrestrials for considerably less than 100 years.
Secondly, based on our own experience, the particular type of insanity that leads to a technological culture depletes resources. Why would any "intelligent" life form want to invade a depleted planet? It make very little sense to me.
Thirdly, a lot of the concern about being invaded is the result of conditioning from early, and perhaps most sci-fi stories. "War of the Worlds" was probably the first, was it?
Finally, unless they are really advanced and have learned some really neat physics tricks that are beyond our understanding, we are not going to encounter them, cause space is big... really, really big...
Al.