DDoS protection strategies in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the first step in DDoS protection.

HLD

The initial step in DDoS protection is to [1] incoming traffic to detect unusual patterns.

Drag options to blanks, or click blank then click option'

Aignore

Bmonitor

Cblock all

Dredirect

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing to block all traffic immediately without analysis.

Ignoring traffic patterns and missing the attack signs.

The first step is to monitor traffic to identify abnormal spikes that may indicate a DDoS attack.

2fill in blank

medium

Complete the code to specify a common method to filter malicious traffic.

HLD

A common method to filter malicious traffic is to use [1] lists that block known bad IP addresses.

Drag options to blanks, or click blank then click option'

Agrey

Ballow

Cwhite

Dblack

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing blacklist with whitelist.

Using greylist which is less common in DDoS filtering.

Using blacklists helps block IP addresses known to be sources of attacks.

3fill in blank

hard

Fix the error in the description of a DDoS mitigation technique.

HLD

One effective technique is [1] routing, which distributes traffic across multiple servers to avoid overload.

Drag options to blanks, or click blank then click option'

Aanycast

Bsingle

Cunicast

Dbroadcast

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing unicast which sends traffic to a single destination.

Choosing broadcast which sends traffic to all nodes, increasing load.

Anycast routing sends traffic to multiple locations, helping balance load and mitigate DDoS attacks.

4fill in blank

hard

Fill both blanks to complete the description of rate limiting in DDoS protection.

HLD

Rate limiting controls the [1] of requests a user can make and [2] excessive traffic from a single source.

Drag options to blanks, or click blank then click option'

Anumber

Bblocks

Callows

Dtime

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'allows' instead of 'blocks' for the second blank.

Confusing 'time' with 'number' for the first blank.

Rate limiting sets the number of allowed requests and blocks traffic exceeding that limit to prevent overload.

5fill in blank

hard

Fill all three blanks to complete the description of a layered DDoS defense strategy.

HLD

A layered defense includes [1] filtering, [2] detection, and [3] response to attacks.

Drag options to blanks, or click blank then click option'

Atraffic

Banomaly

Cautomated

Dmanual

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'manual' response which is slower than automated.

Confusing anomaly detection with traffic filtering.

Layered defense uses traffic filtering, anomaly detection, and automated response to quickly and effectively stop attacks.

Practice

1. Which of the following is a primary goal of DDoS protection strategies?

easy

A. Keep the service available during attack

B. Increase the number of incoming requests

C. Slow down legitimate user traffic

D. Disable firewalls to allow all traffic

Solution

1. Step 1: Understand the purpose of DDoS protection

   DDoS protection aims to prevent attacks from making a service unavailable by handling malicious traffic.

2. Step 2: Evaluate each option against this purpose

   Increasing requests or slowing legitimate traffic harms availability. Disabling firewalls reduces security. Only keeping service available matches the goal.

3. Final Answer:

   Keep the service available during attack -> Option A

4. Quick Check:

   DDoS protection = Keep service available [OK]

Hint: DDoS protection means keeping service up, not blocking all traffic [OK]

Common Mistakes:

• Confusing DDoS protection with traffic blocking
• Thinking DDoS protection increases traffic
• Assuming firewalls should be disabled during attacks

2. Which component is commonly used to distribute incoming traffic and help mitigate DDoS attacks?

easy

A. Load balancer

B. Cache server

C. Database server

D. Application server

Solution

1. Step 1: Identify components that manage traffic

   Load balancers distribute incoming requests across multiple servers to prevent overload.

2. Step 2: Match component to DDoS mitigation role

   Load balancers help absorb and spread traffic, reducing attack impact. Other options do not distribute traffic.

3. Final Answer:

   Load balancer -> Option A

4. Quick Check:

   Traffic distribution = Load balancer [OK]

Hint: Load balancers spread traffic to avoid overload [OK]

Common Mistakes:

• Confusing cache or database servers as traffic distributors
• Thinking application servers handle traffic distribution
• Ignoring the role of load balancers in DDoS defense

3. Consider a system using a CDN and a firewall with rate limiting. Which of the following best describes the request flow during a DDoS attack?

medium

A. Requests go directly to the origin server, bypassing CDN and firewall

B. CDN absorbs traffic, firewall filters requests, then origin server processes allowed requests

C. Firewall blocks all requests, CDN caches nothing

D. Origin server handles all requests before CDN and firewall

Solution

1. Step 1: Understand CDN and firewall roles

   CDNs cache content and absorb traffic near users. Firewalls filter malicious requests before reaching origin.

2. Step 2: Trace request flow during attack

   Requests first hit CDN, which reduces load. Firewall then filters suspicious traffic. Only allowed requests reach origin server.

3. Final Answer:

   CDN absorbs traffic, firewall filters requests, then origin server processes allowed requests -> Option B

4. Quick Check:

   Request flow = CDN -> Firewall -> Origin [OK]

Hint: Traffic flows CDN -> Firewall -> Origin server during attack [OK]

Common Mistakes:

• Assuming requests bypass CDN or firewall
• Thinking firewall blocks all requests indiscriminately
• Believing origin server handles all traffic first

4. A system uses IP blacklisting to block attackers, but legitimate users are still affected. What is the likely issue?

medium

A. Firewall is disabled

B. Blacklist is empty, no IPs blocked

C. Blacklist is too broad, blocking shared IPs

D. System does not log blocked IPs

Solution

1. Step 1: Analyze impact of IP blacklisting

   Blacklisting blocks specific IPs. If too broad, it may block IPs shared by many users.

2. Step 2: Identify why legitimate users are affected

   Blocking shared IPs causes collateral damage to good users. Other options do not explain this effect.

3. Final Answer:

   Blacklist is too broad, blocking shared IPs -> Option C

4. Quick Check:

   Legitimate users blocked = Broad blacklist [OK]

Hint: Too broad blacklist blocks good users too [OK]

Common Mistakes:

• Assuming empty blacklist blocks users
• Ignoring shared IP usage in blacklisting
• Thinking firewall status causes this issue

5. You design a DDoS protection system combining CDN, rate limiting, and real-time traffic analysis. Which approach best balances user experience and attack mitigation?

hard

A. Apply strict rate limits globally, blocking many users during spikes

B. Allow all traffic and rely on origin server capacity

C. Disable CDN and rely only on manual IP blocking

D. Use CDN to absorb traffic, apply adaptive rate limits based on analysis, and alert admins on anomalies

Solution

1. Step 1: Evaluate each strategy's impact on users and attack defense

   Strict global limits block many users, hurting experience. Disabling CDN or manual blocking is slow and risky.

2. Step 2: Identify balanced approach

   Using CDN to absorb traffic reduces load. Adaptive rate limits adjust to traffic patterns, minimizing false blocks. Real-time alerts enable quick response.

3. Final Answer:

   Use CDN to absorb traffic, apply adaptive rate limits based on analysis, and alert admins on anomalies -> Option D

4. Quick Check:

   Balanced DDoS defense = CDN + adaptive limits + alerts [OK]

Hint: Combine CDN, adaptive limits, and alerts for best balance [OK]

Common Mistakes:

• Applying strict limits without adaptation
• Ignoring CDN benefits
• Relying only on manual blocking or server capacity