A method (300) and system for preventing private information to be collected and sent to the INTERNET without the consent of a user of a client computer. Every time the user wishes (317) to run a new application program, an isolator engine is invoked (303). The isolator engine intercepts (329) all the output operations (327) of the application program attempting to send messages to the INTERNET. Each message is compared (330-345) with a privacy list storing a series of strings (such the name of the user, his or her private e-mail address); if a match occurs, the user is asked (352) whether he or she desires to continue or abort execution of the application program.