Denial of Service (DoS/DDoS) in Cybersecurity - Step-by-Step Execution

Concept Flow - Denial of Service (DoS/DDoS)

Attacker sends many requests

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Target server receives requests

↓

Server tries to respond

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Server resources get overloaded

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Legitimate users cannot access service

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Service disruption

The attacker floods a server with excessive requests, causing it to overload and stop serving real users.

Execution Sample

Cybersecurity

Attacker -> send flood of requests
Server -> receive requests
Server -> process requests
Server -> resources overload
Users -> cannot access service

Shows the step-by-step flow of a DoS attack causing service disruption.

Analysis Table

Step	Action	Effect on Server	Effect on Users
1	Attacker sends many requests	Server starts receiving high traffic	Users can access normally
2	Server processes requests	Server CPU and memory usage increase	Users still can access
3	Requests flood continues	Server resources near limit	Users experience slow responses
4	Server resources overloaded	Server cannot handle new requests	Users cannot access service
5	Service disrupted	Server becomes unresponsive or crashes	Users denied access

💡 Server resources fully overloaded, legitimate user requests blocked, causing denial of service

State Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Server CPU Usage	Low	Medium	High	Maxed Out	Overloaded
Server Memory Usage	Low	Medium	High	Maxed Out	Overloaded
User Access	Normal	Normal	Slow	Blocked	Denied

Key Insights - 3 Insights

Why does the server stop responding even though it tries to process requests?

Because the server's CPU and memory reach their maximum capacity (see execution_table step 4), it cannot handle any more requests, causing it to become unresponsive.

Why do legitimate users experience slow responses before being completely blocked?

As the server resources get heavily used (execution_table step 3), it slows down processing all requests, affecting legitimate users before fully denying access.

Is the attack successful if the server never crashes but users cannot access the service?

Yes, the goal of DoS is to deny service, so even if the server stays running but blocks users (execution_table step 5), the attack succeeds.

Visual Quiz - 3 Questions

Look at the execution_table at which step does the server start to block legitimate users?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Check the 'Effect on Users' column in execution_table rows for when users start being blocked.

According to variable_tracker, what happens to server CPU usage after step 3?

A It becomes high

B It stays medium

C It decreases

D It is maxed out

💡 Hint

Look at the 'Server CPU Usage' row in variable_tracker after step 3.

If the attacker sends fewer requests, how would the 'User Access' variable change in variable_tracker?

A It would immediately be 'Denied'

B It would remain 'Normal' longer

C It would become 'Blocked' earlier

D It would not change at all

💡 Hint

Consider how fewer requests affect server load and user access in variable_tracker.

Concept Snapshot

Denial of Service (DoS) attacks flood a server with excessive requests.
This overloads server resources like CPU and memory.
Legitimate users experience slow or no access.
Distributed DoS (DDoS) uses many sources to amplify the attack.
Goal: disrupt service availability to real users.

Full Transcript

Denial of Service (DoS) attacks happen when an attacker sends a huge number of requests to a server. The server tries to handle all these requests, which uses up its CPU and memory. As the server gets overloaded, it slows down and eventually cannot respond to real users. This causes legitimate users to lose access to the service. In a Distributed Denial of Service (DDoS), many attackers or devices send requests together, making the attack stronger. The main idea is to make the service unavailable to real users by overwhelming the server.