Online song-swapping is very popular
The company behind Morpheus, Streamcast Networks, said in a statement that there had never been a security breach in Morpheus since its introduction in April 2001.
The exploit, first reported by BBC News Online, appears to be a result of the way people have set up the program.
It means that potentially millions of people who have downloaded Morpheus may be accidentally sharing more files on their computer than they intended.
Leading file-sharing expert Jack Spratts said: "It seems to be a vulnerability exclusively for those inexperienced enough to share entire drives."
"For those caught unaware, this exploit can be catastrophic, regardless of how much responsibility they share in their own misfortune," he told BBC News Online.
Sharing too much
Morpheus works by allowing people to share files on their computer and swap them over the internet.
When people download Morpheus, they are advised to place the files that they want to share in their My Shared Folder within the program.
This ensures that the user does not inadvertently share something private, as all files in shared folders are accessible by any other Morpheus users.
However, Stuart Moore, who runs SecurityTracker.com, said: "It appears that many people have set up the program to share the entire C: drive, whether by accident or on purpose."
Keeping files private
Using the exploit discovered by the members of the 2600 group, anyone could pry into the computer of a Morpheus user who is sharing their entire hard drive.
But in a statement, Streamcast said it "reminds its users to be sure they are not sharing files they want to keep private or files that are copyrighted".
"Morpheus provides the best user experience available due to its ease of use, rapid download capabilities and persistent data.
"Streamcast is very committed to providing this technology product to consumers to give them a way to communicate and share information directly," the company said.
Morpheus is one of the most popular file-sharing programs. It has been downloaded over 60 million times in just 10 months.