In August of 2003, I posted an article that suggested the SETI folks ought to look at our own DNA to see if there happens to be a hidden message from aliens in there waiting to be discovered. Putting a message in human DNA, particularly in the junk DNA regions, is guaranteed (a) not to degrade significantly over long periods of time and (b) to be found by humans when we reached a suitable level of technological development, and (d) to go with each of us wherever we went on earth and beyond. So, thinking like an alien, DNA would be a much better place to leave a message for future humans than just about anywhere else. Now, the well-known science writer, Paul Davies has come up with the exact same suggestion.
By the way, I wouldn't be surprised if we look and actually find just such a message. Most likely it will read, "Property of Microsoft Corporation, patent-pending" or something to that effect.