Port Scan Attacks

Posted by in Security+ | 0 comments

If you’re planning on taking the Security+ exam, you should have a basic understanding of port scan attacks.

For example, can you answer this question?

Q. You want to identify all of the services running on a server. Which of the following tools is the BEST choice to meet this goal?

A. Penetration test

B. Protocol analyzer

C. Sniffer

D. Port scanner

More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation is available at the end of this post.

Anatomy of an Attack

From a defensive perspective, it’s valuable to understand how attackers operate. Many penetration testers use similar methodologies, so you can also apply this knowledge to penetration testing. Although there is no single definition that identifies all attackers, one thing is clear: Attackers are sophisticated and clever. They should not be underestimated.

Imagine an organization that has unlimited funds to launch attacks. They could be government employees employed by another country, or they could be a group of criminals. They may be trying to steal secrets or steal some of the millions of dollars that attackers are pocketing from businesses and individuals monthly. How will they go about it?

They often combine reconnaissance with fingerprinting techniques to identify targets. Reconnaissance provides a big-picture view of a network, including the Internet Protocol (IP) addresses of a target network. Fingerprinting then homes in on individual systems to provide details of each. Some of the attackers may be experts on reconnaissance, while others are experts on different elements of fingerprinting. Once they identify their targets, attackers use this information to launch an attack.

Identifying Open Ports with a Port Scanner

One group in the organization takes the list of IP addresses and identifies open ports on each system. As a reminder, many protocols use well-known ports. For example, Telnet uses port 23 and Hypertext Transfer Protocol (HTTP) uses port 80. If a port scanner detects port 80 is open, it’s likely that the HTTP protocol is running and it may be a web server.

Port Scan

Additionally, ports also identify applications running on a system. For example, peer-to-peer (P2P) software, used for file sharing, uses specific ports for communications with other peers on the Internet. A port scan can discover these ports and detect P2P software running on a system.

A common Transmission Control Protocol (TCP) port scan sends a TCP SYN (synchronize) packet to a specific port of a server as part of the TCP three-way handshake. If the server responds with a SYN/ACK (synchronize/acknowledge) packet, the scanner knows the port is open. However, instead of completing the three-way handshake, the scanner can send an RST (reset) packet to reset the connection and then repeat the process with a different port.

CompTIA Security+ Study Guide

The 501 Version of the Study Guide

The CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide is an update to the top-selling SY0-201, SY0-301, and SY0-401 study guides, which have helped thousands of readers pass the exam the first time they took it.  It includes the same elements readers raved about in the previous three versions.

Each of the eleven chapters presents topics in an easy to understand manner and includes real-world examples of security principles in action.

You’ll understand the important and relevant security topics for the Security+ exam, without being overloaded with unnecessary details. Additionally, each chapter includes a comprehensive review section to help you focus on what’s important.



Over 300 realistic practice test questions with in-depth explanations will help you test your comprehension and readiness for the exam. The book includes:

  • A 75 question pre-test
  • A 75 question post-test
  • Practice test questions at the end of every chapter.

Each practice test question includes a detailed explanation to help you understand the content and the reasoning behind the question. You’ll be ready to take and pass the exam the first time you take it.

If you plan to pursue any of the advanced security certifications, this guide will also help you lay a solid foundation of security knowledge. Learn this material, and you’ll be a step ahead for other exams. This SY0-501 study guide is for any IT or security professional interested in advancing in their field, and a must-read for anyone striving to master the basics of IT security.

Kindle edition also available.

Even though it’s not recommended for services to use ports other than the well-known ports for specific services, it is possible. Because of this, an open port doesn’t definitively say the related service or protocol is running.

Some port scanners send additional queries to the system’s open ports. For example, if port 25 is open, indicating it’s running Simple Mail Transfer Protocol (SMTP), the scanner can send SMTP queries to the system and analyze the response. These queries provide verification that the protocol is running and often include additional details on the system. Similarly, HTTP queries can identify if it’s a Windows Internet Information Services (IIS) web server or an Apache web server running on a Linux system.

Security+ Practice Test Questions

SY0-501 Practice Test Questions 

Over 300 realistic Security+ practice test questions

All questions include explanations so you'll know why the correct answers are correct,

and why the incorrect answers are incorrect.

Pass the Security+ Exam

the First Time You Take It

Multiple quiz formats to let you use these questions based on the way you learn.
  • Learn mode - randomized. View each of the questions in random order. Learn mode allows you to keep selecting answers until you select the correct answer. Once you select the correct answer, you'll see the explanation. Click here to see how learn mode works.
  • Learn mode - not randomized. View each of the questions in the same order. Use this if you want to make sure that you see all of the questions. Learn mode allows you to keep selecting answers until you select the correct answer. Once you select the correct answer, you'll see the explanation. Click here to see how learn mode works.
  • Test mode - randomized. View each of the questions in random order. In test mode, you can only see the correct answers and explanations after you complete the test. Click here to see how test mode works.
  • Test mode - not randomized. View each of the questions in the same order. In test mode, you can only see the correct answers and explanations after you complete the test. Click here to see how test mode works.
  • Test mode - 75 random questions. View 75 random questions from the full test bank similar to how the Security+ exam has a potential maximum of 75 multiple choice questions. In test mode, you can only see the correct answers and explanations after you complete the test. Click here to see how test mode works.

Get the full bank of SY0-501 Practice Test Questions Here

 SY0-501 Practice Test Questions


INCLUDES QUESTIONS TO HELP YOU PREPARE

FOR THE NEW PERFORMANCE BASED QUESTIONS 

Bonus - Performance Based Questions

Three sets of performance-based questions including over 30 questions. These questions show you what you can expect in the live exam. They include drag and drop, matching, sorting, and fill in the blank questions. See a demo here.

Bonus - Extra Practice Test Questions

New multiple-choice questions in the extra test bank. Questions are added occasionally. You can see what has been added recently here.

Get the full bank of Security+ (SYO-501) Practice Test Questions Here

Get the full bank of Security+ Practice Test Questions

Click here if you're looking for SY0-501 Full Study Package

Each open port represents a potential attack vector, so by identifying open ports, attackers can determine the attack surface. As a reminder, you can reduce the attack surface by disabling all unused services and removing all unneeded protocols. This is a key step in hardening a system, or making it more secure from the default configuration.

Many vulnerability-scanning tools like Nmap, Netcat, and Nessus include port-scanning abilities and scan systems to determine open ports. Security professionals use these tools for vulnerability scans within their networks, but attackers also use these same tools. In addition to scanning for open ports, these tools can also fingerprint a system.

Remember this

A port scanner can help determine what services and protocols are running on a remote system by identifying open ports. Port scanners typically take additional steps to verify the port is open.


Full Security+ Course

SY0-501 Full Security+ Course

Helping you Pass the First Time

Online access includes all of the content from the

CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide

  • Introduction
  • About the exam (including information on the number of questions, test duration, passing score, types of questions and more. Also includes a listing of the exam objectives)
  • 75 question pre-assessment exam
  • Mastering Security Basics (full content from Chapter 1 of the study guide including the exam topic review and 15 practice test questions)
  • Understanding Identity and Access Management (full content from Chapter 2 of the study guide including the exam topic review and 15 practice test questions)
  • Exploring Network Technologies and Tools (full content from Chapter 3 of the study guide including the exam topic review and 15 practice test questions)
  • Securing Your Network (full content from Chapter 4 of the study guide including the exam topic review and 15 practice test questions)
  • Securing Hosts and Data (full content from Chapter 5 of the study guide including the exam topic review and 15 practice test questions)
  • Comparing Threats, Vulnerabilities, and Common Attacks (full content from Chapter 6 of the study guide including the exam topic review and 15 practice test questions)
  • Protecting Against Advanced Attacks (full content from Chapter 7 of the study guide including the exam topic review and 15 practice test questions)
  • Using Risk Management Tools (full content from Chapter 8 of the study guide including the exam topic review and 15 practice test questions)
  • Implementing Controls to Protect Assets (full content from Chapter 9 of the study guide including the exam topic review and 15 practice test questions)
  • Understanding Cryptography and PKI (full content from Chapter 10 of the study guide including the exam topic review and 15 practice test questions)
  • Implementing Policies to Mitigate Risks (full content from Chapter 11 of the study guide including the exam topic review and 15 practice test questions)
  • 75 question post-assessment exam
  • Glossary

Get the SY0-501 Full Security+ Course Here


Test your readiness with these quality materials

Random 75-question tests

Random practice tests from the all of the practice test questions in the CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide. All questions include explanations so you'll know why the correct answers are correct, and why the incorrect answers are incorrect.

3 sets Performance-based Questions

Three new sets of performance-based questions with a total of 30 questions. These new questions use a new testing engine that includes realistic drag and drop, matching, sorting, and fill in the blank questions.

Flashcard Set

  • 494 Online Security+ Glossary Flashcards
  • 222 Online Security+ Acronyms Flashcards
  • 223 Online Security+ Remember This Slide from the popular CompTIA Security+ Get Certified Get Ahead: SY0-501 Study Guide

Audio - SY0-501 Security+ Remember This Audio Files

Learn by Listening. Over one hour and 20 minutes of audio (MP3 downloads.)

Audio - SY0-501 Security+ Question and Answer Audio Files

Learn by Listening. Over two hours hour and 53 minutes of audio (MP3 downloads.)

Bonus #1

Audio from the end of chapter reviews from each of the chapters in the CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide. Over one hour and 40 minutes of additional audio.

Bonus #2

Access to all of the online content that is available for free to anyone that purchases the CompTIA Security+ Get Certified Get Ahead: SY0-501 Study Guide. This includes labs, extra practice test questions, and supplementary materials

Bonus #3 

Access the study materials for a total of 60 days because sometimes life happens.

Get the SY0-501 Full Security+ Course Here

Q. You want to identify all of the services running on a server. Which of the following tools is the BEST choice to meet this goal?

A. Penetration test

B. Protocol analyzer

C. Sniffer

D. Port scanner

Answer is D. A port scanner identifies open ports on a system and is commonly used to determine what services are running on the system.

A penetration test attempts to exploit a vulnerability.

A protocol analyzer (also called a sniffer) could analyze traffic and discover protocols in use, but this would be much more difficult than using a port scanner.

See Chapter 8 of the CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide for more information on checking vulnerabilities.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

CompTIA Security+ Get Certified Get Ahead: SY0-501 Study Guide

Subscribe To Our Newsletter

Join our mailing list and get a free excerpt of the CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide.  This excerpt includes the introduction and Chapter 1. 

You have Successfully Subscribed!

Get Certified Get Ahead is a participant in the Amazon Services LLC Associates Program,
an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.

Copyright © 2015 Get Certified Get Ahead. All Rights Reserved.