Module 01 Denial-of-Service (DoS)

We’ve all been there.

You go to one of your frequently visited websites to:

  • shop online
  • get the latest news or
  • read up on your favorite celebrity

but, inexplicably, you
can’t connect to the site.

If you’re wondering what’s going on
behind the scenes, it’s likely a Denial-of-Service attack.

A Denial-of-Service (DoS) Attack

This attack uses a single
computer or internet
connection to populate a
targeted site or system with
falsified activity, traffic, and
requests, which overload the
site and prevent legitimate
users from getting through.

Distributed Denial-of-Service (DDoS) Attack

A DDoS attack is similar and has the same result, but it uses multiple computers and internet connections—typically thousands or even hundreds of thousands—to overload target servers and deny access to would-be visitors.

Dig In.

Individual, small attacks can be combined to create a major incident.

Here are some examples of DoS/DDoS Attacks:
  1. Botnets
  2. Zombies


A “bot” is a type of malware that allows an attacker to take control of an affected computer during a DoS/DDoS attack. A network of these infected machines is a “botnet,” and can grow to include victim computers across the globe. And it’s not just computers that are at risk.

The Internet of Things (IoT)—a term used to describe any devices connecting to the internet that aren’t primarily computers, from hydroelectric turbines and industrial sensors to home thermostats, kitchen appliances, and medical device monitors—has become a favorite target for hackers.

Poor security practices in the billions of IoT devices that we’ve grown to love make them particularly vulnerable to creating a network of compromised devices.


This is a bot-infected computer connected to the internet that a hacker uses to remotely perform malicious tasks.

Most owners of “zombie” computers are unaware that their system is being used in this way, but there are indications that you’ve been infected, like slower performance, unexplained error messages, and frequent crashes.

Get Real.

The Mirai botnet is estimated to control up to 1.5 million devices on the IoT, mainly through everyday online consumer items, like digital IP cameras and home wireless routers.

This dangerous
international network
is responsible for generating record-setting
DDoS attacks.

These include shutting
down the website
of cyber-crime journalist
Brian Krebs, infiltrating
French web host OVH, and

shutting down large swaths of internet services in Europe and North America during the Dyn attack.

The massive speed and scale with which the Mirai botnet can carry out an attack is a major threat—and it’s still active.

Knowledge Check Module 1


Use what you’ve learned about DoS/DDoS attacks to select the best answer to the following questions.

    1. Your Chosen Answer: Your Chosen Answer:

  • Select a module below to continue.

    Click the previous arrow to review the Knowledge Check.