Editing Wiretapping (section)

===Official use===
{{Main|Lawful interception}}
The contracts or licenses by which the state controls [[Telephone company|telephone companies]] often require that the companies must provide access to tapping lines to law enforcement. In the U.S., telecommunications carriers are required by law to cooperate in the interception of communications for law enforcement purposes under the terms of [[Communications Assistance for Law Enforcement Act]] (CALEA).<ref>{{USPL|103|414}} {{cite wikisource |title=Communications Assistance for Law Enforcement Act of 1994 |wslink=Communications Assistance for Law Enforcement Act of 1994 }}</ref>

When [[telephone exchange]]s were mechanical, a tap had to be installed by technicians, linking circuits together to route the audio signal from the call. Now that many exchanges have been converted to digital technology, tapping is far simpler and can be ordered remotely by computer. This central office switch wiretapping technology using the Advanced Intelligent Network (AIN) was invented by Wayne Howe and Dale Malik at BellSouth's Advanced Technology R&D group in 1995 and was issued as US Patent #5,590,171.<ref>{{cite patent |country=US |number=5590171 |title=Method and apparatus for communications monitoring |pubdate=1996-12-31 |fdate=1995-08-21 |invent1=Wayne Howe |invent2=Dale Malik |assign1=Bellsouth Corporation |status=patent}}</ref> [[Public switched telephone network|Telephone service]]s provided by [[cable TV]] companies also use digital switching technology. If the tap is implemented at a [[digital switch]], the switching computer simply copies the digitized bits that represent the phone conversation to a second line and it is impossible to tell whether a line is being tapped. A well-designed tap installed on a phone wire can be difficult to detect. In some places, some law enforcement may be able to even access a mobile phone's internal microphone even while it isn't actively being used on a phone call (unless the battery is removed or drained).<ref>{{Cite news |url=http://news.cnet.com/2100-1029_3-6140191.html |title=FBI taps cell phone mic as eavesdropping tool |last=McCullagh |first=Declan |date=2006-12-04 |work=CNET |access-date=2010-06-24 |quote=The FBI appears to have begun using a novel form of electronic surveillance in criminal investigations: remotely activating a mobile phone's microphone and using it to eavesdrop on nearby conversations. […] Kaplan's opinion said that the eavesdropping technique "functioned whether the phone was powered on or off." Some handsets can't be fully powered down without removing the battery; for instance, some Nokia models will wake up when turned off if an alarm is set.}}</ref> The noises that some people believe to be telephone taps are simply [[crosstalk]] created by the [[coupling (electronics)|coupling]] of signals from other phone lines.<ref>{{Cite web |url=http://www.privacyrights.org/fs/fs9-wrtp.htm |title=Fact Sheet 9: Wiretapping and Eavesdropping on Telephone Calls |date=May 2010 |website=Privacy Rights Clearinghouse |url-status=dead |archive-url=https://web.archive.org/web/20120111100456/http://www.privacyrights.org/fs/fs9-wrtp.htm |archive-date=2012-01-11 |access-date=2011-12-20}}</ref>

Data on the calling and called number, time of call and duration, will generally be collected automatically on all calls and stored for later use by the [[invoice|billing]] department of the phone company. These data can be accessed by security services, often with fewer legal restrictions than for a tap. This information used to be collected using special equipment known as ''[[pen register]]s'' and ''[[trap and trace device]]s'' and U.S. law still refers to it under those names. Today, a list of all calls to a specific number can be obtained by sorting billing records. A telephone tap during which only the call information is recorded but not the contents of the phone calls themselves, is called a ''pen register'' tap.

For telephone services via digital exchanges, the information collected may additionally include a log of the type of communications media being used (some services treat data and voice communications differently, in order to conserve bandwidth).

{{See also|Carnivore (FBI)}}