Beware of the DOS attack! - That Computer Engineer

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Tuesday, April 24, 2018

Beware of the DOS attack!

Hello fellas! Do you know about that largest DDoS attack on GitHub(2015). Just die already, if you are a computer engineer and still don't know about git hub. One more of such a large scale was on BBC(2015), where its entire domain was down for three hours. Bang! that is one big attack.
A simple DoS attack against a web page of a company results in a huge loss in revenue. This can be fatal for the company revenue as well as the hard earned reputation.

If you don't know what a DoS or a DDoS attack is, don't worry we are here to the rescue. Let's get a raw understanding of the concept before getting into technicalities.

Consider a scenario where you want to contact your best friend Manchander Singh. But one guy named Ziyan keeps on calling him again and again. As a result, when you try to call, you get a busy response. Thus, Ziyan is preventing you from contacting Manchander. This can be related to what we technically call as Denial of Service (DoS) attack. But remember this was just an explanation so that you can understand the concept better.

How a normal conversation takes place

Manchander: Hey                    (Initiation)
Ziyan: Hello!                            (acknowledging )
Manchander: Whats up?          (conversation established)

How communication packets(information or data) are transferred 

Host A: send a TCP SYN packet to host
Host B: receives SYN and sends an SYN-ACK acknowledgement packet.
Host A: receives the ACK 

This establishes the connection. (TCP connection)

Denial of service (DoS) is an attack in which a user is prevented from communicating with a resource by either disabling the resource or hindering the path providing connection.

Possible examples


  1. Unavailability of a resource(e.g a website)
  2. Slow performance  
  3. A sudden increase in spam emails you receive


Common DoS Targets


  1.  Back End Resources
  2.  Web Server 
  3.  Network or Computer specific 

How this can be done?
  1. User requests for a page. But the attacker will make the user go to some other page.
  2. An attacker can close an open port and make it unavailable to the user.
  3. Exhausting all the resources that were earlier kept for the user.
  4. Tricking the machine into crashing or reducing its performance.
  5. Exploiting weakness in TCP/IP ICMP transmission of packets.

This was all about the DoS attack. Let's understand the much dangerous DDoS attack, that is, distributed denial of service attack.

DDOS Attack

Same function but a larger scale. By using a remote network of botnets, it will be used to attack the victim.

Think of this as Night King from The Game of Thrones with an ability to control the white walkers and also create them. The white walkers (zombies) can then be controlled to attack the victim.

A DDoS can also be a diversion for some other attack.

Example: 
  1. UK National Lottery Website (30 September 2017)
  2. Boston Globe
  3. Hong Kong Democracy movement

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