LUDs
local usage details; a list of locally called numbers, often provided by telecom companies to the police as part of an investigation.
LUDs: call records that show who dialed whom and when
A Local Usage Detail, or LUD, is a telephone company's record of calls made from or received at a specific line. The record shows the calling number, called number, date, time, and duration of each call, but not the content of the conversation. Telephone service providers generate these records automatically as part of normal network operation and billing. Law enforcement and authorized parties can request LUDs as evidence in criminal investigations, civil litigation, or regulatory proceedings.
LUDs are distinct from other call metadata. A phone bill shows summarized usage by category and cost; a LUD is a detailed line-by-line log of individual calls. They are equally distinct from toll records, which historically referred to long-distance calls only. Modern LUDs typically include local, long-distance, mobile, and international calls made from a given number, depending on the service provider's infrastructure and what the requesting party is authorized to access.
Legal and technical scope
In the United States, law enforcement typically obtains LUDs under subpoena, court order, or (in emergency cases) with verbal consent followed by formal documentation. The specificity of a LUD request varies: investigators may ask for all calls on a line during a date range, calls to or from a specific number, or calls to a geographic area code. Wireless carriers maintain separate LUD records for incoming and outgoing calls; some distinguish between voice, text message, and data sessions.
The format and retention period of LUDs differ across carriers. Most retain detailed records for 12 to 24 months; some maintain archived records longer. A typical LUD entry includes the originating number, terminating number, date (sometimes with millisecond precision), call duration in seconds, and a code indicating call outcome (completed, busy, no answer, etc.). Some carriers record the cell tower or routing information as well, which can be used for location analysis separate from the call metadata itself.
LUDs are valuable in criminal investigations because they establish pattern and association: who contacted whom, how often, and when. They are also routinely used in civil disputes over business dealings, custody matters, and communications-related employment cases. The term LUD is less common in daily speech than in legal and law enforcement documents; many carriers refer to them internally as CDRs (call detail records) or simply as account records.