(1) Authorization attack: some person who is authorized
to use some system or information resource for some
purpose converts the authorization into other nonauthorization
purposes, which is also called “internal attack”.
The “trigger” which is set in some system or some
component permits the violation of security policy upon
input of special data.
(2) Horse Attack: the software contains a harmful
program segment which can not be detected, which could
damage the user’s security upon its execution. This
application program is called Trojan Horse. Computer virus:
a program which could realize functions of transmission and
attack during operation of computer systems.
(3) Human Factors: an authorized person divulges
information to a non-authorized one for the sake of interest
or due to his carelessness. The information is obtained from
wasted disks or printed storage media. The invader bypasses
the physical control and gains access to the system.
Important goods for security, such as tokens or identity cards
are stolen. Business deception: some forged system or
system component cheats legal users or systems into
willingly abandoning sensitive information, etc.