I’ve just read the so called “paper” on Extra Terrestrials and it is the worst kind of nonsense and may as well be prepared by primary school kids given the lack of any knowledge or ability to draw inferences from human history let alone any concept of what really might happen if alien lifeforms ever contacted us.
Why do civilisations make forays into the wilderness?

1. For political esteem (exploration) – the Romans, Greeks, Egyptians and Chinese are recorded as sending missions well beyond their boarders. Whilst there were other benefits, what we clearly see in the historical accounts are these missions being used to bolster political regimes control of power at home. Even the moon landings fall into this category (not mentioned in paper)
2. For political esteem (conquest). It is well known that the Romans “conquered” Scotland several times and each and every time it seems the conquest was carried out for the political esteem of “conquest of the remotest lands” rather than for economic or other obvious benefit (although to repress troublesome tribes may be a practical outcome)
3. For economic resources. If there are resources that are valuable enough to transport from the wilderness missions will attempt to secure them. The simplest resources are biological … new plant species, new food species, it only takes a handfull of seeds and a whole agricultural industry worth billions can be created. That is why the British sent Captain Cook down to the south seas and as I recall one great success was Sago (why?)

As far as I can see this paper knows nothing of earth’s history. OK, the motivation for other species may be different, but the fundamental laws of economics remain the same, and power politics does reflect human motivations, but most advanced species will share many of those motivations so human history is a far better place to start than the imagination of Star trekies.
Ignoring the bleedingly obvious
My next criticism is that like all “scientists”, the people writing this paper simply ignore the bleedingly obvious.
Look at the ceiling!! What do you see? Look at the sky (at night) what do you see? Look down a telescope in any urban environment … what do you see?
Human created light! Light – mostly sodium at very specific frequencies, modulated at very tight frequencies which are various harmonics of 5Hz light that is millions billions trillions? of times larger than any of the stupid “beacons to extraterrestrial life”.
Indeed, if any alien were to look at the bleedingly obvious signal of human created light and the signals from all that mains cabling and its harmonics, the one conclusion they will draw is that:
The world is controlled by two empires/religions, one based on the 60Hz “faith” and the other on 50Hz. They will then be able to plot the progression and growth of each empire draw fabulous “representations” of the churches of the 50Hz and 60Hz religions and no doubt show the high priests of the religions in their coats of flashing colours with tenticles hanging out. (joke)
Now, if one really wanted to communicate with aliens on another planet the solution is simple: to use low frequency modulation of the mains (ideally all one frequency) this would not only alter the predominate sodium spectrum main modulation frequency of street lights, it would also affect all the massive output of mains noise from all those unsuppressed motors and spikes and clitches which continually inject harmonics of mains into the radio spectrum to the annoyance of anyone trying to capture the feeble signals of “scientists” monitoring extra terrestrials and people with real jobs like communications engineers.
In other words, it wouldn’t do to suggest that humans are already shoving so much energy into space through modulated sodium street lights that there is absolutely no need to spend even a penny on “scientists” sending any more signals which no alien is going to be looking for because they will be looking for actual evidence of advance civilisations like …. street lighting, electricity and fossil fuel residues in the atmosphere.
Computer viruses
What a bunch of idiots! A computer virus is specific to the processor, it requires an intimate knowledge of the code and the way that code runs in the operating system. The idea that human civilisation could catch a computer virus from aliens is literally as stupid as humans catching a computer virus!
What is more likely is that alien life may be based on the same DNA as (most) earth life. Now computers can’t catch an alien virus because aliens don’t have our computers and their unique instructions sets, but they could have our DNA and they could bring viruses that are far more virulent than those found on earth … but the risk is low because viruses need to defeat the particular cell defence mechanisms and at such a complex level it is likely that lifeforms differ. However, that very difference may mean viruses have novel (primitive) invasive techniques which are not replicated in any earth viruses.
Alien Contact … a one way ticket for the aliens!
But, when it comes to bacteria or similar, then we are really in for trouble. Given the huge variation of such lifeforms on earth, and the likely prevalence of such lifeforms on alien planets, it is highly risky for physical contact. Indeed, I would doubt that any alien visitors would be allowed to return to their homeland given the risk of bringing new hostile bacteria, fungus etc back with them.
Irrespective of the time it would take to travel to earth, irrespective of the problems sending a probe that can not only travel to earth but back again, the real problem for any possible aliens is that they simply cannot allow aliens to return from an “infected” planet. Raw materials like rare earths, or rare isotopes could be returned in heat treated containers that destroy any possible infections, ideas could be sent, but not living creatures – although perhaps plants (particularly food plants like wheat?) and smaller organisms could be specially disinfected, but not whole bodies … or perhaps with specially designed suits … even then the risk is far too big!
But I’m forgetting the stupidity of politicians … who could deny the victory parade as the great explorer sent by emperor alienus the III returns showing the great power of yet another tyrant and their unchallengeable position of dominance.

Addendum – communicating with Aliens

Let’s imagine you have just travelled across half the Galaxy to another planet and you are just about to open the door what is your major concern:
mathematics: 1+1 = 2
Chemistry: Is there O2 in the atmosphere to breath and any trace gases that are poisonous.
Biology: what infections are there
So, let’s try communicating on the first: K K KK … comprendez? Maths might be a universal “language”, but it has nothing to talk about. No one except nerds at University just talk about maths, we use maths as a tool it is a means to understand other things and without any context it is useless.
So what of biology. Of course we want to know about biology … unfortunately, biology is probably very specific to any planet, so whereas Maths is universal but has nothing to talk about, biology has everything to talk about but no commonality (although breathing, eating and defecating would be topics most aliens would understand).
Chemistry … specifically atmospheric gases, the content of water, food. YES! Indeed, we already have a perfect vocabulary … the periodic table. OK, perhaps it is drawn differently, but it wouldn’t take long to understand and to share a mutually useful language …. of which the most likely first sentence would be … can I trade something for more O2? Or do you have H2O?
Of course, the real use would be a few inquiries of relative abundance of rare elements … materials which might just  be abundant enough on earth to make it economic to travel half way across the galaxy!