The trojan has been labelled "ransomware" because it uses malicious code to hijack user files and to encrypt them so they cannot be accessed. It then asks for payment in return for the decryption key.
Louisa Heran, "PC file kidnappers demand ransom," Sydney Morning Herald, March 15, 2006
Elizabeth Millard, "New Trojan Kidnaps Files for Ransom," Sci-Tech Today, March 17, 2006
Security researchers at San Diego-based Websense uncovered the unusual extortion plot when a corporate customer they would not identify fell victim to the infection, which encrypted files that included documents, photographs and spreadsheets. ...
The FBI said the scheme was unlike other Internet extortion crimes. Leading security and antivirus firms this week were updating protective software for companies and consumers to guard against this type of attack, which experts dubbed "ransomware."
Ted Bridis, "Internet infection holds files hostage," The Associated Press, May 25, 2005