Virus makes file-sharing program share files

AP reports that there is a new computer virus that finds files on Winny users' PCs and makes them available to others by sharing them:

The malware, called Antinny, finds random files on Winny users' PCs and makes them available on the file-sharing network. So far, the data leaked have been varied and plentiful: passwords for restricted areas at airports, police investigations, customer information, sales reports, staff lists.

The constantly updated virus seems to have spared no one — airlines, local police forces, mobile phone companies, the National Defense Agency. Even an antivirus software manufacturer has suffered.

Who in their right mind would put file-sharing software on the same machine that has secret investigation documents?