or valuable asset. The revolution of mobile applications and wireless communication make possible to get notified by your phone, when your properties are stolen. Probably the first solution of mobile application based theft detection is BluCop, which was published in December 2010. Preventing removal of items Yet another method is the attachment of items to a larger immobile object, usually furniture or walls. Disabling the stolen item Items with specific functionality can often be disabled to prevent use of the item should it be stolen. The anti-theft system can require disabling on every use, or enabling when the item should be secured. Disabling the anti-theft system is usually done by requiring identification of the owner at some stage of use. Identification can occur physically or through other methods (physical keys, numerical codes, complex passwords, biometric identification). This can work even retrospectively: as a stolen credit card can easily be invalidated with a phone call to the issuing bank, the motivation to steal one is reduced. In the case of vehicle theft, the best deterrent to theft is in the installation of an approved vehicle anti-theft passive immobilizer. Many vehicles have factory-installed anti-theft units, which provide protection through the ignition system. Under the hood there is a computer that controls the operation of the engine. It is programmed to verify that the RFID tag attached to the key is correct before the ECM will allow ignition to occur. An approved immobilizer uses a three circuit isolation system which thwarts even the most experienced thief. Security tags Security tags are devices that are attached to products to prevent shoplifting and are often used in conjunction with an electronic article surveillance system. SelectaDNA or Smartwater are such security tags - a forensic fluid which contains millions of tiny fragments which have a unique number called "SIN" ("SelectaDNA identification number"), and registered in a national police database together with the owner's details, is etched into each of those particles. Tracking software Electronic devices such as laptops, cell phones and even gadgets such as iPods now have software that enable them to "phone home" with information regarding their whereabouts and other information that can assist law enforcement in tracking down the devices. Forensic marking Assets can be marked with various forensic marking materials for law enforcement tracking of the item. Examples of this type of marking include SelectaDNA and Smartwater. See also Danish bicycle VIN-system