Introduction

Security affects all the layers that we have talked about:

• In the Data link layer, we will talk about wireless security.
• In the Network Layer, we will talk about Firewalls and VPNs (Virtual Private Network).
• In the Transport Layer, we will talk about Tor (The Onion router) and TLS (Transport Layer Security).
• Finally in the Application Layer we will talk about DNS security, Multi-factor Authentication and Email and Instant Messaging security.

Wireless Security (Data Link Layer)

Goals

Wireless communication is particularly vulnerable to attacks, as it is very to easy to get and intercept a wireless communication. For example, if there was no security, we could simply block other signals with ours, listen to all communications (unless there is some additional encryption on top of it), impersonate other devices by changing your MAC address in the frames, etc.

We will look at the scenario where someone is talking to a wireless router, and there is some Malory (that is, a malicious party which passively spies, etc., the users, without changing messages or anything similar).

The goals that we want to achieve some security are:

• Data integrity. We want to make sure that the data we sent to the wireless router is not changed by Malory.
• Confidentiality of content. You should not allow Malory to take a look into what you are sending.
• Access control. Not allow anyone to join the network and take your bandwidth. E.g., limiting to to employees of your organization, household members, etc.

Wireless Encryption Protocol (WEP)

This was the first protocol ever made for Wireless. It is fundamentally a broken protocol; extremely easy to break it.

The idea was: