"Using contact chaining," Olsen wrote, "N.S.A. may be able to discover previously unknown telephone identifiers used by a known terrorist operative . . . to identify hubs or common contacts between targets of interest who were previously thought to be unconnected, and potentially to discover individuals willing to become US Government assets".
An index of a file is much like an index of a book; it consists of a listing of identifiers that distinguish the records (e.g., names might be used to identify personnel records), along with the records' locations.
The Guardian can reveal an employee of the agency inadvertently sent the passport numbers, visa details and other personal identifiers of all world leaders attending the summit to the organisers of the Asian Cup football tournament.
But all of the photographs had identifiers embedded within them and the numbers of regime facilities where the people had been killed.
The officer wrote that it was "unlikely that the information is in the public domain", and said the absence of other personal identifiers "limits significantly" the risk of the breach.
There has long been talk of using biometric identifiers such as fingerprints or face-recognition technology to add an extra layer of security, but these have yet to catch on widely.And even if they were to become more widespread, they would not protect firms from rogue staff.
To do so, it needs to know their likes and purchases as well as their identifiers and demographics, including name, sex, age, address, current location and income bracket.
For its part, KISSmetrics assures that identifiers were not exchanged among unrelated sites.
A group dubbed "AntiSec", which is affiliated with Anonymous, a prominent group of hackers, has leaked a file containing over 1m unique device identifiers (UDIDs) from the tech giant.
But the FBI has publicly pooh-poohed this claim in turn, saying it never had the identifiers and that reports that one of its laptops has been compromised are "totally false".
