The Spy software or spyware are malicious or misleading applications that are inadvertently installed together with other programmes that are downloaded by the user. Said types of programmes can perform various different actions: there are those dedicated to the collection of information in the system they are installed in, to later send it via Internet.

Others are dedicated to showing continuous undesired publicity or to changing visualized pages or those non-existent in the original. All these activities are hidden behind confusing authorizations, for which reason the user is not aware of them.

Other defects of the most intrusive spyware is that they can change our principal page for another, chosen by the spy programme, that can be either a blank page or one of dubious content. On attempting to restore the principal page through options offered by the Explorer, it can be found to be impossible. The changes made by the spy in the system’s registers will not allow it. To avoid inconvenience caused by this type of spy programme, it is advisable to use anti-spy programmes. Said programmes function in a similar way to the antivirus programmes, but they analyse the system in their search for spy programmes and eliminate them. They are not incompatible with antivirus programmes, but are complementary. If both are installed in the computer we will be protected well against possible intrusions into our system.