<P> According to Edward Snowden, the US National Security Agency has a system that tracks the movements of everyone in a city by monitoring the MAC addresses of their electronic devices . As a result of users being trackable by their devices' MAC addresses, Apple has started using random MAC addresses in their iOS line of devices while scanning for networks . If random MAC addresses are not used, researchers have confirmed that it is possible to link a real identity to a particular wireless MAC address . </P> <P> Many network interfaces (including wireless ones) support changing their MAC address . The configuration is specific to the operating system . On most Unix - like systems, the ifconfig command may be used to add and remove "link" (Ethernet MAC family) address aliases . For instance, the "active" ifconfig directive may then be used on NetBSD to specify which of the attached addresses to activate . Hence, various configuration scripts and utilities allow to randomize the MAC address at boot or network connection time . </P> <P> Using wireless access points in SSID - hidden mode (see network cloaking), a mobile wireless device may not only disclose its own MAC address when traveling, but even the MAC addresses associated to SSIDs the device has already connected to, if they are configured to send these as part of probe request packets . Alternative modes to prevent this include configuring access points to be either in beacon - broadcasting mode, or probe - response with SSID mode . In these modes, probe requests may be unnecessary, or sent in broadcast mode without disclosing the identity of previously - known networks . </P> <P> The standard (IEEE 802) format for printing MAC - 48 addresses in human - friendly form is six groups of two hexadecimal digits, separated by hyphens (-) in transmission order (e.g. 01 - 23 - 45 - 67 - 89 - ab). This form is also commonly used for EUI - 64 (e.g. 01 - 23 - 45 - 67 - 89 - ab - cd - ef). Other conventions include six groups of two hexadecimal digits separated by colons (:) (e.g. 01: 23: 45: 67: 89: ab), and three groups of four hexadecimal digits separated by dots (.) (e.g. 0123.4567. 89ab); again in transmission order . </P>

The mac address of an access point is referred to as the