Lawful Intercept – Existing Global
Models
Several key global reference
models for Lawful Interception are found in the reports, technical
specifications, and standards of the European Telecommunication Standards
Institute. Essentially all national
implementations follow these models in-so-far as communications provider and
associated Law Enforcement Agency functions are concerned.
Overall LI Model[1]
1) A LEA requests lawful authorization from an
authorization authority, which may be a court of law.
2) The authorization authority issues a lawful
authorization to the LEA.
3) The LEA passes the lawful authorization to
the communications provider. The communications provider determines the
relevant target identities from the information given in the lawful
authorization.
4) The communications provider causes
interception facilities to be applied to the relevant target identities.
5) The communications provider informs the LEA
that the lawful authorization has been received and acted upon. Information may be passed relating to the
target identities and the target identification.
6) Information Related Information (IRI) and
Content of Communication (CC) are passed from the target identity to the communications
provider.
7) IRI and Content of Communication are passed
from the communications provider to the Law Enforcement Monitoring Facility
(LEMF) of the LEA.
8) Either on request from the LEA or when the
period of authority of the lawful authorization has expired the communications
provider will cease the interception arrangements.
9) The communications
provider announces this cessation to the LEA.
Communication Provider Functions[2]
The
communication of data elements from the Communication Provider to the Law Enforcement
Monitoring Facility are described in terms of three types of Handover
Interfaces.
HI1 - Administration
The
administration interface will have to be standardized towards the authorities
that issue orders for interception, in order for the interception management to
work smoothly. National laws will have provisions for this. The HI1 interface
is often paper-based, but it can be anticipated that electronic transfer of
data and automated activation/deactivation of interceptions will become more
common in the future. There is also a need to find a standard for translation
between external HI1 protocols and the internal network interfaces towards
vendor-specific equipment. Many operators use equipment from several vendors
and it is in their interest to be able to handle this in a uniform way, through
a common management system.
HI2 - Intercept Related Information
IRI
is sent to the LEMF as a result of LI-related events in the communication. Such
events may also lead to establishment or disconnection of a content delivery
channel on the HI3 interface.
HI3 - Contents of Communication
Delivery
of call contents is initiated and discontinued based on specific LI-related
events in the communication. The communication contents data stream will
correspond to the intercepted identity. If for instance an e-mail address is
used as target for interception, the contents will be delivered to the LEMF as
e-mail. If the interception triggers on ATM channel identity, an ATM data
stream will be delivered.
Communications Provider – LEA
Interfaces[3]
The generic Handover Interface adopts a three port
structure such that administrative information (HI1), intercept related
information (HI2) and the Content of Communication (HI3) are logically
separated. The figure above shows a
block diagram with the relevant entities for Lawful Interception. The outer
circle represents the Communication Providers domain with respect to lawful
interception. It contains the network internal functions, the internal network
interface (INI), the administration function and the mediation functions for
IRI and CC. The inner circle contains the internal functions of the network
(e.g. switching, routing, handling of the communication process). Within the
network internal function the results of interception (IRI, CC) are generated
in the IIF.
The internal interception functions (IIF) provide
the Content of Communication (CC) and the intercept related information (IRI),
respectively, at the internal network interface INI. For both kinds of
information, mediation functions may be used, which provide the final
representation of the standardized Handover Interfaces at the Communication
Provider’s domain boundary.
Within the Communication Provider’s administration
centre, the LI related tasks, as received via interface HI1, are translated
into man machine commands for the provider’s equipment.