Many illegal file-sharers view themselves as the "Robin Hoods of the digital age", a researcher said today.
Joe Cox, of the University of Portsmouth Business School, has examined the motivations and behaviours of different types of people who illegally download and share music and video on the internet.
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Using a survey of 6,103 people in Finland, he found that many who share files feel they are motivated by a sense of altruism and a desire for notoriety.
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Of the respondents, 95% were male and the average age was 28.
File-sharing, the transfer of files from one computer to another over a network, allows a number of people to make exact copies of the same file.
Mr Cox said: "Some file-sharers see themselves as masked philanthropists - the Robin Hoods of the digital age.
"They believe their activities shouldn't be considered illegal, which means finding the most appropriate form of deterrence and punishment is extremely difficult.
"Although it is difficult to measure the true extent of how illegal file-sharing has affected the creative industries, I do believe it is a significant threat in terms of loss of employment and revenues."
For his research, published in the academic journal Information Economics and Policy, Mr Cox separated file-sharers into two types -
"leechers" and "seeders".
Leechers are those who download digital media illegally from other parties, but who are not explicitly making content available in return.
Seeders are those who have acquired the material in the first instance and are making it available to leechers.
He said: "It's a fascinating area to research because the seeders who are sharing the material appear to have little obvious gain and are certainly not doing it for any financial reward.
"My research shows they are motivated by feelings of altruism, community spirit and are seeking recognition among other members of the file-sharing community.
"I think it's likely some benefit is also derived from a feeling of 'getting one over on the system' too.
"Seeders seem to consider the expected cost of punishment to be minimal, which is largely due to the low perceived likelihood of detection.
"It's as if they believe the peer esteem they'll generate from their infamy will outweigh any of the costs associated with their activities."