- A
It uses MS-CHAPv2 authentication which is susceptible to brute-force attacks
MS-CHAPv2 has known vulnerabilities and can be cracked.
- B
It relies on IKE for key exchange
Why wrong: PPTP does not use IKE; it uses its own key management.
- C
It uses MPPE encryption which is considered weak
MPPE uses RC4, which is deprecated.
- D
It supports strong authentication with digital certificates
Why wrong: PPTP does not support certificate-based authentication.
- E
It provides perfect forward secrecy
Why wrong: PPTP does not provide forward secrecy.
Question 763 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network administrator is reviewing the security of the company's VPN solution. They discover that the current VPN uses PPTP. Which TWO of the following are significant security weaknesses associated with PPTP?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It uses MS-CHAPv2 authentication which is susceptible to brute-force attacks
PPTP uses Microsoft Point-to-Point Encryption (MPPE), which relies on the RC4 stream cipher. RC4 has known weaknesses, including statistical biases and the ability to recover plaintext after encrypting a large volume of traffic, making it considered weak for modern security requirements. Additionally, PPTP's default authentication protocol is MS-CHAPv2, which is vulnerable to offline brute-force attacks because its challenge-response mechanism uses a weak DES-based hash that can be cracked with tools like Asleap or ChapCrack.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It uses MS-CHAPv2 authentication which is susceptible to brute-force attacks
Why this is correct
MS-CHAPv2 has known vulnerabilities and can be cracked.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
It relies on IKE for key exchange
Why it's wrong here
PPTP does not use IKE; it uses its own key management.
- ✓
It uses MPPE encryption which is considered weak
Why this is correct
MPPE uses RC4, which is deprecated.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
It supports strong authentication with digital certificates
Why it's wrong here
PPTP does not support certificate-based authentication.
- ✗
It provides perfect forward secrecy
Why it's wrong here
PPTP does not provide forward secrecy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse PPTP's use of MPPE with stronger encryption protocols like IPsec, or mistakenly think that MS-CHAPv2 is secure because it uses a challenge-response mechanism, overlooking its fundamental reliance on weak DES encryption and the NT hash.
Detailed technical explanation
How to think about this question
The MS-CHAPv2 protocol uses a 16-byte challenge and response that is derived from the user's NT hash (MD4 of the password). The response is encrypted with DES using a key derived from the hash, which reduces the effective keyspace to 2^56, making it feasible to brute-force offline with tools like John the Ripper. MPPE uses RC4 with a 40-bit or 128-bit key, but the key is derived from the same MS-CHAPv2 session key, so compromising the authentication directly compromises the encryption. In practice, a captured PPTP handshake can be cracked in minutes on modern hardware, as demonstrated by the EAPHammer and Asleap tools.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It uses MS-CHAPv2 authentication which is susceptible to brute-force attacks — PPTP uses Microsoft Point-to-Point Encryption (MPPE), which relies on the RC4 stream cipher. RC4 has known weaknesses, including statistical biases and the ability to recover plaintext after encrypting a large volume of traffic, making it considered weak for modern security requirements. Additionally, PPTP's default authentication protocol is MS-CHAPv2, which is vulnerable to offline brute-force attacks because its challenge-response mechanism uses a weak DES-based hash that can be cracked with tools like Asleap or ChapCrack.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jul 4, 2026
This CISSP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISSP exam.
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