Downgrade Attack

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We recently added the following downgrade attack Security+ practice test question to the online test banks. Can you answer it?

Q. A web server has the newest TLS cryptographic protocol suite installed. However, you recently discovered it is susceptible to downgrade attacks. What should be done to ensure that systems use the MOST secure connections by default?

A. Replace the existing certificate with a new one.

B. Implement OCSP.

C. Reconfigure the cipher suite order.

D. Rekey the existing certificate.

Do you know the answer? 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.

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CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide

  • Introduction
  • About the exam (including types of questions and strategies for performance-based questions)
  • 100 question pre-assessment exam
  • Mastering Security Basics (full content from Chapter 1 of the study guide including the exam topic review and 20 practice test questions)
  • Exploring Control Types and Methods (full content from Chapter 2 of the study guide including the exam topic review and 20 practice test questions)
  • Understanding Basic Network Security (full content from Chapter 3 of the study guide including the exam topic review and 20 practice test questions)
  • Securing Your Network (full content from Chapter 4 of the study guide including the exam topic review and 20 practice test questions)
  • Securing Hosts and Data (full content from Chapter 5 of the study guide including the exam topic review and 20 practice test questions)
  • Understanding Malware and Social Engineering (full content from Chapter 6 of the study guide including the exam topic review and 20 practice test questions)
  • Identifying Advanced Attacks (full content from Chapter 7 of the study guide including the exam topic review and 20 practice test questions)
  • Managing Risk (full content from Chapter 8 of the study guide including the exam topic review and 20 practice test questions)
  • Preparing for Business Continuity (full content from Chapter 9 of the study guide including the exam topic review and 20 practice test questions)
  • Understanding Cryptography (full content from Chapter 10 of the study guide including the exam topic review and 20 practice test questions)
  • Exploring Operational Security (full content from Chapter 11 of the study guide including the exam topic review and 20 practice test questions)
  • 100 question post-assessment exam
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Random 100-question tests

Random practice tests from the all of the practice test questions in the CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide. All questions include explanations so you'll know why the correct answers are correct, and why the incorrect answers are incorrect.

34 Simulated Performance-based Questions

Eight sets of performance-based questions with multiple questions in each set. These questions help you understand and prepare for performance based questions.

22 Realistic Performance-based Questions

Two new sets of performance-based questions with a total of 22 questions. These new questions use a new testing engine that includes realistic drag and drop, matching, sorting, and fill in the blank questions.

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Subnetting mini-tutorial that will help you answer two key question types:
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Access the study materials for a total of 60 days because sometimes life happens.

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Downgrade Attack

A downgrade attack is a type of attack that forces a system to downgrade its security. The attacker than exploits the lesser security control. It is most often associated with cryptographic attacks.

The common example is with Transport Layer Security (TLS) and Secure Sockets Layer (SSL). SSL has known vulnerabilities and has been replaced with TLS in most implementations. However, many servers have both SSL and TLS installed. If a client is unable to use TLS, the server will downgrade its security and use SSL.

Attackers exploit this vulnerability by configuring their systems so that they cannot use TLS. When they communicate with the server, the server uses SSL instead of TLS. This allows attackers to launch SSL-based attacks such as the Padding Oracle On Downgraded Legacy Encryption (POODLE) attack.

Note: The POODLE attack is a man-in-the-middle type of attack. It exploits systems that can switch to SSL instead of using TLS exclusively.

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Modify the Protocol List to Prevent Downgrade Attack

One way to ensure that SSL isn’t used on a site is to modify the protocol list and ensure that SSL is disabled. Typically, a site will have the following five options. Disabling SSL 3 and SSL2 will prevent a downgrade attack using SSL 3 or SSL 2.

  • TLS 1.2
  • TLS 1.1
  • TLS 1.0
  • SSL 3
  • SSL 2

Note that this list is configured at the server level and there are multiple ways to do so. For example, on an Apache server, you can typically access this via a server Control Panel, modifying the Web Services Configuration. The following graphic shows the TLS/SSL protocols, under the TLS/SSL Cipher List.

cipherprotocol

Note that the configuration is coded:

  • SSLv23 indicates SSL all, or all versions of SSL.
  • !SSLv2 is code for Not SSLv2.
  • !SSLv3 is code for Not SSLv3.
  • TLS versions are not mentioned, but are enabled.

Modify the Cipher Suite List to Prevent Downgrade Attack

The cipher list is simply a list of predefined cipher suites. The previous figure showed part of the title for one cipher suite in the TLS/SSL Cipher list. However, the setting includes many more. For reference, here is a list of a few cipher suites.

  • TLS_RSA_WITH_AES_256_GCM_SHA384 (0x9d)
  • TLS_RSA_WITH_AES_128_GCM_SHA256 (0x9c)
  • TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x33)
  • TLS_RSA_WITH_AES_128_CBC_SHA256 (0x3c)
  • TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (0x9e)

The Cipher Suites blog discusses these in more depth (and includes a sample Security+ practice test question).

An important consideration with the cipher suite list is the order. When a client attempts a secure connection with a server, they both negotiate the most secure cipher protocol and cipher suite that both systems support. Normally, this works effectively.

However, what if an attacker configures his system to only support legacy or insecure cipher suites? If the server supports a legacy cipher suite, it may be the most secure suite that both support. The attacker can then connect with this older suite and exploit it. To avoid this vulnerability, the cipher suite list should omit legacy and deprecated cipher suites.

Are Your Servers Vulnerable?

Qualys SSL Labs has created an online SSL Server Test you can use to check your server.  Just plug in the URL here. Here’s what you want to see.

sslgradea

Security+ Practice Test Questions

SYO-401 Practice Test Questions Now Available

Over 440 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.

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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.
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 SYO-401 Practice Test Questions Now Available


INCLUDES QUESTIONS TO HELP YOU PREPARE

FOR THE NEW PERFORMANCE BASED QUESTIONS 

Bonus - Performance Based Questions

Additional Security+ questions to help you prepare for the new performance based questions. These are included with the full bank of Security+ practice test questions and are divided into different sections. For example, you'll have access to the following links:

- Performance Based Question - Set 1

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of security to mobile devices and servers in a data center. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 2

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 3

You'll see a graphic showing a network with computers and servers separated by a firewall. The firewall is used to control traffic between the computers and users using rules within an access control list (ACL).  You'll have three questions that test your knowledge and ability to correctly identify the relevant components of the rule. The incorrect answers and explanation provide you with insight into how to correctly answer this type of question on the actual exam.

- Performance Based Question - Set 4

You'll see a graphic explaining what you might be required to do on the actual exam related to what a forensic analyst would do during an investigation. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 5

You'll see a graphic explaining what you might be required to do on the actual exam to match protocols and ports. You'll then have seven questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 6

You'll see a list of security controls along with a graphic showing devices and locations within an organization, along with instructions on what you might be required to do on the actual exam to match the controls with the devices and locations. You'll then have four questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 7

You'll see a list of authentication methods and authentication factors along with instructions on what you might be required to do on the actual exam to match the authentication methods with the authentication factors. You'll then have six questions that test your knowledge and ability to correctly answer the questions. This set also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 8

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This is similar to Set 2 but expands on the possibilities. The set also includes a link to a page showing the end solution for the overall performance based question simulation.

New - Performance Based Question - Set 9

New questions recently added using a different testing engine. See a demo here. This set includes drag and drop and matching questions on ports.

New - Performance Based Question - Set 10

A random set of 20 performance-based questions using drag and drop, matching, sorting, and fill in-the blank. This set includes performance-based questions on RAID.

Get the full bank of Security+ Practice Test Questions Here

Get the full bank of Security+ Practice Test Questions


So, can you answer this question?

Q. A web server has the newest TLS cryptographic protocol suite installed. However, you recently discovered it is susceptible to downgrade attacks. What should be done to ensure that systems use the MOST secure connections by default?

A. Replace the existing certificate with a new one.

B. Implement OCSP.

C. Reconfigure the cipher suite order.

D. Rekey the existing certificate.

C is correct. You should reconfigure the cipher suite order and ensure that legacy cipher suites are not supported. By reconfiguring the cipher suite order to use the strongest suites first, it ensures that systems will negotiate using the strongest cipher suites. Additionally, it’s possible to omit legacy and deprecated cipher suites from the cipher suite list.

While not available as a possible answer, it is also possible to ensure that older legacy protocols (such as SSL 2 and SSL3) are not supported.

A is incorrect. The cipher suite order is not configured in the certificate so replacing the certificate won’t help with this scenario.

B is incorrect. The Online Certificate Status Protocol (OCSP) is used to verify the health of a certificate. It wouldn’t select the best cipher suite.

D is incorrect. Rekeying a certificate creates a new certificate with the same name and expiration date (but new keys). However, the certificate doesn’t determine what protocol or cipher suite will be used.

See Chapter 10 of the CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide for more information on cipher suites.

CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide

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