Prank callers can now be easily found through Caller ID, so it is often asserted that prank calls since the 1990s have been harder to accomplish and thus waning in popularity.[4] Most telephone companies permit callers to withhold the identifying information from calls using the vertical service code *67 that blocks the caller’s ID (141 in the UK), but potential victims may be reluctant to answer a call from an ID-blocked number.[4] Wiretapping by several governments have also helped bypass this problem. Callers can also call from payphones in order to hide their identity, although this is becoming less common as pay phones are beginning to phase out starting in the late 2000s. The advent and advancements in digital switching technologies such as those found in SS7, unspoofable ANI, as well as outbound and inbound calls being logged at carrier exchange equipment, further complicate the pranksters will to remain anonymous while carrying out such activities.Another increasingly popular option is to use some form of VoIP. With some VoIP services, the telephone number will simply not exist. These calls are extremely difficult to trace since they may pass through servers and routers operated by multiple corporations or entities in various countries. Although law enforcement agencies may theoretically be able to find where a VoIP call originates from if they tried, in practice the amount of time, effort, and resources required would be too great to use on ordinary prank calls.