As we've mentioned before, the network software always
consists some bugs and gaps, so the hackers often take
advantage of them to make the intrusion, steal the information
or damage the data. Comparing to the threats from the hackers,
the attacks they made are more active and harmful, including
nondestructive ones and destructive ones. The nondestructive
attacks disturb the normal operation of the network system,
while the destructive attacks intrude the computer system to
damage or steal the target. The frequent ways the hackers use
are the following: attacking the E-mail, stealing password,
using the defects to cheat and using of Trojan Horse attack and
viruses.