AWS WAF for web application firewall - Step-by-Step Execution

Process Flow - AWS WAF for web application firewall

Start: Web Request Received

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AWS WAF Inspects Request

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Check Against Rules

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Match

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Block or Allow

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Request Sent to Web Application

AWS WAF checks each web request against rules and decides to block or allow it before it reaches your web app.

Execution Sample

AWS

1. Receive web request
2. Inspect request with AWS WAF
3. Match request against rules
4. If match, block or allow
5. Forward allowed requests

This flow shows how AWS WAF processes a web request to protect your web application.

Process Table

Step	Action	Request Detail	Rule Match	Decision	Result
1	Receive request	GET /login	N/A	N/A	Request received
2	Inspect request	Headers and IP checked	N/A	N/A	Inspection started
3	Check rule 1	IP blocklist	No	Continue	No match, check next
4	Check rule 2	SQL injection pattern	Yes	Block	Request blocked
5	Decision made	Block request	Yes	Block	Request denied, no forward
6	End	Request blocked	N/A	N/A	Request stopped at WAF

💡 Request blocked at step 5 due to matching SQL injection rule

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Request Status	Received	Inspected	Checked Rule 1	Matched Rule 2	Blocked
Rule Match	None	None	No	Yes	Yes
Decision	None	None	Continue	Block	Block

Key Moments - 2 Insights

Why does the request get blocked even though it passed the first rule?

Because AWS WAF checks all rules in order. The request failed the second rule (SQL injection), so it is blocked as shown in execution_table row 4 and 5.

What happens if no rules match the request?

If no rules match, AWS WAF allows the request to pass through to the web application, as shown in the 'No Match' branch in the concept_flow.

Visual Quiz - 3 Questions

Look at the execution table, what is the decision at step 3?

A Continue checking rules

B Block the request

C Allow the request immediately

D Drop the request silently

💡 Hint

Refer to execution_table row 3 under 'Decision' column

At which step does the request get blocked?

A Step 2

B Step 4

C Step 3

D Step 6

💡 Hint

Check execution_table rows 4 and 5 for when 'Block' decision occurs

If the SQL injection rule was removed, what would happen at step 4?

A Request would be blocked anyway

B Request would be dropped silently

C Request would continue to next rule or allowed

D AWS WAF would crash

💡 Hint

Refer to execution_table row 4 where rule match affects decision

Concept Snapshot

AWS WAF checks incoming web requests against security rules.
If a request matches a blocking rule, it is stopped.
If no rules match, the request passes to your web app.
Rules can block IPs, detect attacks like SQL injection.
AWS WAF protects your app by filtering bad traffic early.

Full Transcript

AWS WAF acts like a security guard for your web application. When a web request arrives, AWS WAF inspects it carefully. It checks the request against a list of rules you set up, such as blocking bad IP addresses or detecting attack patterns like SQL injection. If the request matches a blocking rule, AWS WAF stops it and does not let it reach your web app. If it does not match any rule, the request is allowed through. This process helps keep your web application safe from harmful traffic.

Practice

1. What is the main purpose of AWS WAF (Web Application Firewall)?

easy

A. To store large amounts of data securely

B. To manage virtual machines in the cloud

C. To protect web applications by filtering and blocking harmful web traffic

D. To monitor network bandwidth usage

Solution

1. Step 1: Understand AWS WAF's role

   AWS WAF is designed to protect web applications by filtering incoming HTTP requests based on rules.

2. Step 2: Compare options with AWS WAF function

   Only To protect web applications by filtering and blocking harmful web traffic describes filtering and blocking harmful web traffic, which matches AWS WAF's purpose.

3. Final Answer:

   To protect web applications by filtering and blocking harmful web traffic -> Option C

4. Quick Check:

   AWS WAF = Web traffic protection [OK]

Hint: AWS WAF filters web traffic to protect apps [OK]

Common Mistakes:

• Confusing AWS WAF with storage services
• Thinking AWS WAF manages virtual machines
• Assuming AWS WAF monitors bandwidth

2. Which of the following is the correct way to create a rule in AWS WAF to block requests from a specific IP address?

easy

A. Use AWS Shield to block the IP address

B. Directly add the IP address to the Web ACL without a rule

C. Create a Lambda function to block the IP address

D. Create an IP set with the IP address, then add a rule to block requests matching that IP set

Solution

1. Step 1: Understand AWS WAF rule creation

   In AWS WAF, you create an IP set containing IP addresses, then create a rule that uses this IP set to block matching requests.

2. Step 2: Evaluate options for correctness

   Create an IP set with the IP address, then add a rule to block requests matching that IP set correctly describes creating an IP set and a rule. Options B, C, and D do not follow AWS WAF's process.

3. Final Answer:

   Create an IP set with the IP address, then add a rule to block requests matching that IP set -> Option D

4. Quick Check:

   IP set + rule = block IP [OK]

Hint: Use IP sets with rules to block IPs in AWS WAF [OK]

Common Mistakes:

• Trying to block IPs directly in Web ACL without rules
• Confusing AWS WAF with Lambda or Shield
• Skipping IP set creation

3. Given this AWS WAF rule configuration snippet:
{"Name": "BlockBadBots", "Priority": 1, "Action": {"Block": {}}, "Statement": {"ByteMatchStatement": {"SearchString": "BadBot", "FieldToMatch": {"UriPath": {}}, "TextTransformations": [{"Priority": 0, "Type": "NONE"}]}}}
What will happen when a request URI contains the text "BadBot"?

medium

A. The rule will cause an error and not apply

B. The request will be blocked by AWS WAF

C. The request will be logged but allowed

D. The request will be allowed without filtering

Solution

1. Step 1: Analyze the ByteMatchStatement

   The rule looks for the string "BadBot" in the URI path and blocks the request if found.

2. Step 2: Understand the action on match

   The action is "Block", so any request matching the condition will be blocked.

3. Final Answer:

   The request will be blocked by AWS WAF -> Option B

4. Quick Check:

   Match "BadBot" in URI = block request [OK]

Hint: ByteMatch with Block action blocks matching requests [OK]

Common Mistakes:

• Assuming requests are allowed by default
• Confusing Block with Count or Allow actions
• Thinking the rule causes errors

4. You created an AWS WAF rule to block requests from IP 203.0.113.5, but requests from this IP are still allowed. What is the most likely cause?

medium

A. The Web ACL is not associated with the resource

B. AWS WAF does not support blocking IP addresses

C. The IP address was not added to the IP set used by the rule

D. The rule action is set to Allow instead of Block

Solution

1. Step 1: Check IP set and rule configuration

   If the IP was not added to the IP set or the rule action was wrong, blocking would fail, but these are common mistakes.

2. Step 2: Verify Web ACL association

   Even if rules are correct, if the Web ACL is not linked to the web resource (like CloudFront or ALB), rules won't apply.

3. Final Answer:

   The Web ACL is not associated with the resource -> Option A

4. Quick Check:

   Web ACL association needed for rules to apply [OK]

Hint: Always associate Web ACL with resource to enforce rules [OK]

Common Mistakes:

• Forgetting to associate Web ACL with the resource
• Assuming AWS WAF can't block IPs
• Setting wrong rule action

5. You want to protect your web app from SQL injection and block requests from a list of suspicious IPs. Which AWS WAF setup is best?

hard

A. Create a Web ACL with a managed SQL injection rule group and a custom IP set rule to block suspicious IPs

B. Use only an IP set rule to block suspicious IPs, ignoring SQL injection

C. Create a Lambda function to inspect requests and block SQL injection

D. Enable AWS Shield Advanced to block SQL injection and IPs

Solution

1. Step 1: Identify protection needs

   You need to block SQL injection attacks and block suspicious IP addresses.

2. Step 2: Choose AWS WAF features

   AWS WAF provides managed rule groups for SQL injection and supports IP set rules for blocking IPs.

3. Step 3: Evaluate options

   Create a Web ACL with a managed SQL injection rule group and a custom IP set rule to block suspicious IPs combines managed SQL injection rules and custom IP set blocking, which is best practice. Options B, C, and D do not fully meet requirements or use incorrect services.

4. Final Answer:

   Create a Web ACL with a managed SQL injection rule group and a custom IP set rule to block suspicious IPs -> Option A

5. Quick Check:

   Managed rules + IP sets = full protection [OK]

Hint: Combine managed rules with IP sets for layered protection [OK]

Common Mistakes:

• Using only IP blocking without SQL injection rules
• Relying on Lambda or Shield for WAF tasks
• Not combining rules in one Web ACL