By default, this check occurs every five minutes, plus when Internet Explorer starts; however, the user could configure the next check to occur only at certain times of the day or on certain days of the week. The tool queries the Microsoft server for a file called "codice_1", which contained a list of all the critical updates released for the operating system. The tool then compares this list with the list of installed updates on its machine and displays an update availability notification. Once the check is executed, any custom schedule defined by the user is reverted to the default. Microsoft stated that this ensures that users received notification of critical updates in a timely manner.