Summary: Network Security

Read the summary and the most important questions on Network Security

• Chapter 1

• What is the difference between vulnerability and threat?

  Vulnerability describes the specific weakness that may be exploited, while a threat refers to the event and action exploiting it.

• What is layer 2 in the osi model?

  Data Link Layer, uses raw bit transmission functionality from the physical layer to establish a link between hosts. This layer determines how individual bits are grouped into chunks called frames, and coordinates which network interface may send at any give time if the link is shared among multiple devices. The data link layer also introduces the first level of addressing, assigning identifiers to the physical network adapters, and performs basic detection of transmission errors.

• What can we conclude for the case of encryption in network communication given that encryption is placed high in the OSI layers?

  The higher encryption is placed in the OSI layers, the lower the overall share of the encrypted bits on the wire actually is.
  
  Protocols beneath the encrypting layer add their information after the encryption, which means that all the meta information and headers from the layers below are left in the clear.

• Give the security tradeoff dilemma that you have when looking at what OSI layer you should encrypt data?

  On the one side we would actually like end-to-end conent security (encryption as high as possible). On the other side we want as far reaching meta data protection as possible (encryption as low as possible).

• Give three main factors why cyber crime has suddenly become a major issue.

  1. IT systems and services have reached a very high proliferation.
  2. Attacks on computers and networks don't require a lot of specialized knowledge anymore.
  3. Conducting fraudulent activities online is much less risky than conducting crime in person.

• Chapter 2.1

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• What 2 fundamental techniques are used to transfer data over a cable?

  1. Analog signal - Verifies the amplitude or frequency
  2. Digital signal - Injecting pulses of energy.

• How is the bandwith used efficiently in cables?

  By using frequency division multiplexing. Each connection is mixed with a specific carrier frequency, so both can be transmitted at the same time.

• GIve 2 drawbacks on analog signals.

  1. Not all frequencies are treated equally. Lower frequencies propagate slower than higher ones.
  2. Communication is very susceptible to external noise.

• What technique measures the signal reflections from impedance mismatches?

  Time Domain Reflectometers (TDR).

• What 3 techniques were presented to provide transmission security for wireless signals?

  1. FHSS (Frequency Hopping Spread Spectrum)
  2. Chirps
  3. DSSS (Direct-Sequence Spread Spectrum)