Hackers

1
Hackers
Individuals who gain unauthorized access to
computer systems.

• They can
• Read the data files
• Run the application
• programs
• Modify some files which may cause damages

2
Ways hackers use to invade the computer system

• 1. Tapping
• Information theft can tap into communication line
  and steal the data without interrupting the
  sending and receiving of data.

ADD
Communication media (e.g. network/ telephone
line)
RECEIVER
SENDER
ADD
The message ADD is duplicated by the hacker.
HACKER
3

• To overcome this problem, we can use Data
  Encryption method to help us because it is hard
  or even impossible to impose a physical
  protection or password during this process.

Data Encryption

• Data are usually encrypted before sending and
  decrypted upon receiving.
• A method of converting a meaningful message into
  an encrypted form which does not carry any
  meaning.

http//cd.ed.gov.hk/tech/tech_sub/IT_kit/student/p
hoto/1_6_1e.htm
4
Example Given the encrypted form is HKK.
Knowing this key. Change every letter in the
message to another one.
ADD
ADD
HKK
HKK
Communication media (e.g. network/ telephone
line)
RECEIVER
SENDER
5
2. Denial of Service

• Definition A prevention of the use of
  information resources either intentionally or
  unintentionally, which affects the availability
  of the information resources.
• Hackers send large amount of meaningless messages
  or e-mail to target.
• Make the server not able to react with large
  amount of information at the same time.
• Computer may react very slowly and cause the
  service to stop.

http//cd.ed.gov.hk/tech/tech_sub/IT_kit/c_student
/flash/3_4_a_13b.htm
6
3. Change/ Delete information in a web
site. 4. Transmit computer virus or infected
programs through e-mail. (e.g. I Love You) 5.
Unauthorized use of others password and access
users information without permission.
http//cd.ed.gov.hk/tech/tech_sub/IT_kit/c_student
/flash/3_4_a_13a.htm