4. Communications And Network Security

Question 1

What is the OSI model mnemonic?

Answer 1

All People Seem To Need Data Processing

Question 2

What is the 7th level of the OSI model, and an example?

Answer 2

Application

Example: data

Question 3

What is the 6th level of the OSI model, and an example?

Answer 3

Presentation
Example: data
Present data in a format that all computers can understand.
The ONLY layer without any protocols.
Concerned with (file level) encryption, compression and formatting.

Question 4

What is the 5th level of the OSI model, and an example?

Answer 4

Session
Example: data
Responsible for establishing a connection between two applications (either on the same or different computers).

Question 5

What is the 4th level of the OSI model, and an example?

Answer 5

Transport
Example: segments
Pervades end-to-end data transport between two machines.
Protocols used here: SSL/TLS, TCP, UDP.

Question 6

What is the 3th level of the OSI model, and an example?

Answer 6

Network

Example: packets

Question 7

What is the 2nd level of the OSI model, and an example?

Answer 7

Data

Example: frame, dumb switches.

Question 8

What is the 1st level of the OSI model, and an example?

Answer 8

Physical

Example: bits

Question 9

What are common threats to the 1st level of the OSI model?

Answer 9

Theft, unauthorized access, vandalism, sniffing, data emanation.

Question 10

How do switches in the 2nd layer of the OSI model direct traffic?

Answer 10

They use IP addressing to direct traffic and isolate traffic into broadcast domains.

Question 11

Is a layer 3 switch necessary for inter-VLAN communication?

Answer 11

No, layer 2 switches can perform this function.

Question 12

What are the frequently exploited attacks for layer 3 of the OSI model?

Answer 12

Loki - sending data in ICMP headers(as a covert channel).
Ping of Death - violates the MTU (maximum transmission unit) size.
Ping floods - lots of ping traffic
SMURF - uses spoofed source address (target) and directed broadcasts to launch a DDoS.

Question 13

In what case is UDP better to use then TCP?

Answer 13

When “real time” transfer is essential. Media streaming, gaming, etc.

Question 14

What kind of firewall is at the 3rd layer of the OSI model?

Answer 14

Packet filters

• uses ACL to control access.
• not stateful, just looks at the network and transport layers.

Question 15

What kind of firewall is at the 5th layer of the OSI model?

Answer 15

Stateful Firewalls

- router keeps track of connections table.

Question 16

What kind of firewall is at the 7th layer of the OSI model?

Answer 16

Application Firewalls
- NAT/PAT
—NAT allows one-to-one mapping of IP addresses.
—PAT allows multiple private addresses to share one public address.
- like what is at work.

Question 17

What subnets are set aside for private IP addressing?

Answer 17

10. x.x.x
11. 16.x.x - 172.31.x.x
12. 168.x.x

Question 18

What does POTS stand for?

Answer 18

Plain old telephone system.

Type of circuit switching technology for WAN.

Question 19

What does PSTN stand for?

Answer 19

Public Service Telephone Network. Type of circuit switching for WAN.

Question 20

What does ISDN stand for ?

Answer 20

DSL. It is a type of circuit switching for WAN.

Uses the same lines as phone lines.

Question 21

What kind of packet switching do cable modems use?

Answer 21

MPLS (multi-protocol labeled switching)

Purely layer 3 technology

Question 22

How does VOIP work?

Answer 22

It converts analog to digital through use of telephony adapters or smartphones.
Not designed to be secure.
Greatest threat is eavesdropping.

Question 23

What are the security threats to wireless APs?

Answer 23

Unauthorized access
Sniffing data
War driving
Unauthorized access points.

Question 24

What is the weakest transmission encryption?

Answer 24

WEP - wired equivalent privacy.

Question 25

Describe WEP

Answer 25

It has a weak initialization vector (IV)
IV transmitted in plain text
Uses RC-4 stream cipher
Only option for 802.11b

Question 26

Describe WPA

Answer 26

Wireless protected access
Introduced TKIP
Still uses RC-4

Question 27

Describe WPA2

Answer 27

Wireless Protected Access 2
Introduced AES
Is not backwards compatible with WPA.

Question 28

What are the three main flavors of cloud computing?

Answer 28

Software as a service
Platform as a service
Infrastructure as a service

Question 29

What are the different types of cloud networks?

Answer 29

1. Private
2. Public
3. Community
4. Hybrid (public and private)