Some people have gone through their entire lives adamant that they shared an encounter with a genuine, real-life alien.
Others have produced what they claim is definitive proof of extra-terrestrial life – blurry video clips of mysterious figures, or unexplained images purportedly showing UFOs in the sky.
But for every account that ufologists deem worthy of further investigation, countless hoaxes are invented to shame, embarrass or poke fun at a community desperate to make an historic breakthrough.
These can range from little white lies that are instantly dismissed by experts to scandals that rock the community having been regarded as truthful for decades.
What isn’t a mystery to researchers is why people go to the trouble of attempting to fool them.
According to Philip Mantle, a world renowned UFO researcher and author with 40 years in the field, there are three reasons why people lie about alien sightings.
They are simply to create ‘mischief’, to make money by selling their story to media outlets, or to make UFO experts look gullible and foolish.
Mr Mantle told Metro.co.uk: ‘It can be damaging when a hoax does slip through the net and appears on TV or in newspapers. It does cast a shadow on that subject.
‘There is also a small number of researchers who will never admit it is a hoax.
‘They have such a strong belief that there is no amount of evidence that will prove to them it is a fake.’
Mr Mantle has a ‘guilty until proven innocent’ policy, regarding any ‘evidence’ he receives with the utmost suspicion.
Such an attitude is even more important in an age where anyone can edit or adapt footage and photographs, making cons even harder to uncover.
Mr Mantle added: ‘There needs to be more diligence now then there ever was. But equally, the tools to investigate claims are more readily available.
‘I think those that have been a hoax, I have managed to show that is exactly what they were. But we are all human and they can slip through the net.
‘A lot of them are not deliberate hoaxes but genuine mistakes, or it might be an individual who is sceptical who will conduct a hoax to show how gullible UFO experts are.’
When a possible fake story does slip through the net – and when the suspected hoax is a significant account of one of Britain’s most famous UFO sightings – the repercussions can be seismic.
Larry Warren, who claims he witnessed a UFO landing in Rendlesham Forest, Suffolk in 1980 and later co-authored a book about the incident, has been accused of making the whole thing up.
Mr Warren has stood by his account – but his co-author Peter Robbins has said he feels ‘deceived’ and the publisher of their book has suspended distribution.
Nick Pope, a former UFO expert for the Ministry of Defence, has criticised Mr Warren over the incident.
Describing Mr Warren as an ‘attention-seeker’, Mr Pope said people who make up false stories are ‘crackpots, frauds and charlatans’.
He told Metro.co.uk: ‘While there can be many motivations for hoaxing, the most common one is attention-seeking. It’s a case of the nobody who wants to be a somebody.
‘In relation to UFOs it’s particularly effective because hoaxers are pushing at an open door, given that the UFO community has a strong will to believe.
‘Hoaxers take advantage of this by telling people exactly what they want to hear, shaping their lies to fit people’s existing belief system.
‘Mud sticks, and a single hoax can be remembered long after years of good quality research and investigation have been forgotten. The danger is that people throw out the baby with the bathwater, dismissing the UFO phenomenon as a whole.
‘The exposure of the Larry Warren fraud has damaged the standing of the case itself, even though most of the story is verified by declassified Ministry of Defence documents. But, for a while at least, all people will remember is ‘that guy who made up a crazy UFO story’.’
Cosimo, the publisher of ‘Left at East Gate: A First-Hand Account of the Bentwater-Woodbridge UFO Incident, its Cover-Up, and Investigation’, has suspended distribution of the book.
In a statement, Cosimo said: ‘It has been brought to our attention that some of the experiences described in this book may be inaccurate or embellished.
‘As an independent publisher, we look for quality books in a wide range of genres from public affairs and personal development to history, philosophy and niche subjects such as ufology, and then make a determination whether these books fit well within our catalogue.
‘At this moment, we cannot be certain that Left at East Gate still meets this standard. Consequently, we have decided to suspend the distribution of this book, until the situation surrounding it has been clarified to our satisfaction.’
Mr Warren has insisted his version of events really happened.