🧮 Week 4: Loops and Iteration – “Automating Repetition for Security Tasks”

Learning Objectives

By the end of this week, students will be able to:

1. Understand and use for and while loops effectively.
2. Loop through lists and perform conditional checks on each item.
3. Use loops to process structured security data (like IP addresses).
4. Begin thinking about efficiency and automation in repetitive security workflows.

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🧩 Lecture & Demo Overview

Concept	Description	Short Demo Example
for loops	Iterate over a list or range of items	for i in range(5): print(i)
while loops	Repeat while a condition is true	while x < 5: x += 1
Loop control keywords	break, continue, pass	Demonstrate skipping or stopping
Nested loops	Loops inside loops (simple intro)	Example: iterate users × permissions
Lists and iteration	How lists connect to loops	Show looping over list of IPs

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🧰 Walkthrough Exercise: “Filtering IP Addresses”

Scenario: As a junior SOC analyst, you’ve been given a list of IP addresses from network logs. Your task is to identify which ones are internal (private) vs. external addresses.

Step 1 – Starter Code

# Week 4: Loops and Iteration
# Goal: Identify internal vs external IP addresses

ip_addresses = [
    "192.168.1.25",
    "10.0.0.8",
    "172.16.5.14",
    "8.8.8.8",
    "172.15.3.2"
]

for ip in ip_addresses:
    print(ip)

Ask students: “What does this do?” Then discuss how we can use if statements inside loops to classify.

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Step 2 – Add Conditional Checks

for ip in ip_addresses:
    if ip.startswith("192.168.") or ip.startswith("10."):
        print(f"{ip} is an internal address.")
    else:
        print(f"{ip} is an external address.")

🧠 Teaching Moment: Explain what .startswith() does and why this is an example of automation — imagine having to do this manually for hundreds of log entries.

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Step 3 – Extend to Handle More Cases

for ip in ip_addresses:
    if ip.startswith("192.168."):
        zone = "Private (Class C)"
    elif ip.startswith("10."):
        zone = "Private (Class A)"
    elif ip.startswith("172.16.") or ip.startswith("172.17.") or ip.startswith("172.31."):
        zone = "Private (Class B)"
    else:
        zone = "Public"

    print(f"{ip} → {zone}")

This introduces elif and more structured logic.

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Step 4 – While Loop Challenge

Have students convert part of this logic to a while loop for practice.

Example:

index = 0
while index < len(ip_addresses):
    ip = ip_addresses[index]

    if ip.startswith(("192.168.", "10.")):
        print(f"{ip} is internal.")
    else:
        print(f"{ip} is external.")

    index += 1

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💻 Challenge Tasks

Challenge 1 – Count Internal vs External

Add counters to determine how many internal and external IPs are in the list.

Hint: Use two variables — internal_count and external_count — and increment inside the loop.

Output example:

Internal: 3
External: 2

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Challenge 2 – Store Results in New Lists

Create two lists: internal_ips and external_ips, then append items during iteration.

Stretch: Print the total and show the lists at the end.

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Challenge 3 – Looping from User Input

Allow the user to type IP addresses until they type done, then classify each.

Example:

Enter an IP (or 'done' to finish): 192.168.2.5
192.168.2.5 is internal.
Enter an IP (or 'done' to finish): 8.8.8.8
8.8.8.8 is external.
Enter an IP (or 'done' to finish): done

This reinforces the “while loop until condition” concept interactively.

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🧠 Reflection & Discussion

• Why might a SOC analyst need to separate internal vs external traffic?
• What mistakes could happen if this script were written incorrectly?
• How could this scale to a file with thousands of IPs?

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🧩 Optional Advanced Task (for faster students)

Read IPs from a text file and write results to another file.

with open("ips.txt") as f:
    ip_addresses = f.read().splitlines()

internal_ips = []

for ip in ip_addresses:
    if ip.startswith(("192.168.", "10.")):
        internal_ips.append(ip)

with open("internal_ips.txt", "w") as out:
    for ip in internal_ips:
        out.write(ip + "\n")

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📄 Deliverables

Students should submit:

1. Their Python script (loops_ips.py).
2. Screenshot or copy of successful run output.
3. 2–3 sentence reflection on what loops made easier.

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🧾 Rubric (20 points)

Category	Points	Criteria
Correct use of for loop	5	Loops through all items
Correct conditional logic	5	Correctly identifies internal vs external
Code organization	5	Readable, uses comments
Reflection / explanation	5	Shows understanding of why loops are useful