We won't know if Alien will be hostile like the creatures in V who want to enslave us and use us as a food source or if they will friendly like Vulcans in star Trek until they arrive and show themselves to the general population.
The alleged U.F.O. abductions might give the impression that the aliens are hostile by kidnapping people and subjecting them to experiments including of sexual nature. One of the arguments of alien abductions is that they've come all this way, do a few experiments and then leave.
Professor Stephen Hawkings, one of the greatest living astronomical scientists alive today said in his Discovery programme in 2010 that aliens could well be hostile based on history. Stephen cites what happened when Europeans travelled to the Americas, it didn't end too well for the natives.
If you go back further in time to the time of the Romans, they were among the most technically advanced populations at the time. The Romans were also one of the most aggressive and expansionist, conquering Europe and some parts of Africa and the Middle East.
Aggressive aliens are more likely to create technology that would enable them to cross the cosmos to us. Hopefully not but we do have to have to prepare ourselves for that eventuality. If hostile aliens were the first to arrive, Earth will not go down without a fight. Although we haven't made the push into deep space, we're not going to be a push-over.
We have been pumping out radio signals from our planet for the past hundred or so years so any intelligent civilisation that is within 110 light years from Earth will know we're here. If you'd like to know how far signals from different years have reached, its highly recommended to visit LightYear.FM.
According to the site if you pull back, the earliest signals would just be reaching 49 Librae about now. If amongst those listening were hostile aliens, they could be on their way, we'd have 100 or so years (provided from 49 Librae) to prepare, that is if we haven't blown ourselves up by then. The good news is that the site does say that the signals would be hard to distinguish amongst background noise after a few light years from Earth so if the aliens are unable to filter out our signals then we're safe. It'll also probably explain why we've not heard from anyone yet because we have not filtered the noise out from all the background noise.
The galaxy has about 100 billion stars, give or take, and to choose a star to visit would be guesswork unless you had some clue as to whether its worth visiting or studying from afar. Therefore it will explain why Alien Abductions are a relatively new thing because before our radio signals, it'd be a needle in a haystack kind of search.
The first modern day alien abduction took place on September 19th, 1961 when a couple Betty and Barney Hill driving home on a rural highway near Portsmouth, Hampshire were unable to account for two hours. After investigation, they discovered the cause to be an alien abduction and from then on, reported alien abductions increased. Quartz Media
The opposite type to hostile aliens are the friendly aliens, the ones that want to share information, be our friends etc. The friendly alien is the type that we all hope that will come.
There's few example, in fact I can't think of any where contact between two technologically different groups ended well for the lesser. Just because history doesn't provide a case for this doesn't mean it won't be the case for alien contact.
We'd also have to be careful in case aliens pretend to be our friends like the Visitors did in V but their motives were sinister in the least.
Aliens might know we're here but because we're not advanced enough, they might not be interested in contacting us. Its not a new thought, its one that's been used in Star Trek. In Star Trek, Vulcans only contacted humans once humans had managed faster than light speed. Contacting Earth before we're technically advanced enough would break the first.
If the reported U.F.O. - Unidentified Flying Object are really from outer space and that they've not made real conclusive contact, it would seem that they are disinterested in making contact with us. Either disinterested or a prelude to a much bigger visit.
Conspiracy theorists alleged that aliens have already made contact with U.S. Government and are being held in Area 51 in the Nevada Desert. They believe that a U.F.O. crash landed in Roswell and that the craft was taken away to be studied. If the U.S. Government did have the craft, how comes we've not got very far in terms of technology after years of studying.
There is also a theory that the Government has made contact with aliens but are keeping details of the contact quiet as not to scare people. The Hostile alien theory would be to not alarm the populace. The friendly alien argument is to prevent other governments from gaining the knowledge.
This might disappoint you to hear that there is no conclusion as to which way the aliens go until they arrive. You need to form your own conclusion.