How the RIAA tracks file-sharers

"The disclosures were included in court papers filed against a Brooklyn woman fighting efforts to identify her for allegedly sharing nearly 1,000 songs over the Internet. The recording industry disputed her defense that songs on her family's computer were from compact discs she had legally purchased," reports AP. "According to the documents, the Recording Industry Association of America examined song files on the woman's computer and traced their digital fingerprints back to the former Napster file-sharing service, which shut down in 2001 after a court ruled it violated copyright laws."