Direct Access Test Units (DATUs) are special
PSTN
The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists ...
phone numbers that terminate at the
central office switch
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type o ...
in a telephone company's local exchange that provide switchmen and telco technicians with a circuit for testing lines in various ways.
Among the many things a DATU can do are:
* Make certain electrical connections, such as shorting a line's tip to ring, tip to ground, or ring to ground.
* Play certain tones on the line (high tone, low tone) to test the line's audio circuit.
* Monitor the audio circuit on the line if it is in use (though this only provides a scrambled rendition of the line's audio circuit for privacy and security reasons).
* Create and modify certain variables such as counters and timers on the CO switch, as well as adding and modifying exchanges.
* Remove a line from
permanent signal
Permanent signal (PS) in American telephony terminology, or permanent loop in British usage, is a condition in which a POTS line is off-hook without connection for an extended period of time.Telcordia Technologies, GR-505-CORE Issue 2, December ...
holding state.
DATU's are primarily non-published numbers, though they usually have the phone number XXX-9935 (where XXX represents the local exchange). They are password protected for security, though many telcos leave the
default password
Where a device needs a username and/or password to log in, a default password is usually provided to access the device during its initial setup, or after resetting to factory defaults.
Manufacturers of such equipment typically use a simple passw ...
of 1111 set.
In July 2004,
New York City
New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
phone phreak
Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. The term ''phreak'' is a se ...
William Quinn, also known as "decoder", was arrested and charged with accessing
Verizon
Verizon Communications Inc. ( ), is an American telecommunications company headquartered in New York City. It is the world's second-largest telecommunications company by revenue and its mobile network is the largest wireless carrier in the ...
's DATU numbers on over 100 occasions. Verizon subsequently claimed in press releases that it spent $120,000 to change the passwords on all the DATU numbers (it is unclear if this represented Verizon changing the DATU passwords from the default and if so why this had not been done at time of initial installation).
[http://www.computerworld.com/securitytopics/security/cybercrime/story/0,10801,94512,00.html Computer World, July 13, 2004]
References
Phreaking
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