SY0-501 · Question #350
Which of the following could occur when both strong and weak ciphers are configured on a VPN concentrator? (Select TWO)
The correct answer is A. An attacker could potentially perform a downgrade attack. C. The integrity of the data could be at risk. Configuring a VPN concentrator to support both strong and weak ciphers introduces significant security risks, primarily by enabling downgrade attacks and jeopardizing data integrity.
Question
Which of the following could occur when both strong and weak ciphers are configured on a VPN concentrator? (Select TWO)
Options
- AAn attacker could potentially perform a downgrade attack.
- BThe connection is vulnerable to resource exhaustion.
- CThe integrity of the data could be at risk.
- DThe VPN concentrator could revert to L2TP.
- EThe IPSec payload reverted to 16-bit sequence numbers.
How the community answered
(57 responses)- A81% (46)
- B4% (2)
- D7% (4)
- E9% (5)
Why each option
Configuring a VPN concentrator to support both strong and weak ciphers introduces significant security risks, primarily by enabling downgrade attacks and jeopardizing data integrity.
An attacker can perform a downgrade attack by manipulating the handshake process to force the client and VPN concentrator to negotiate and use a weaker, less secure cipher suite that is still supported.
While resource exhaustion can be an attack vector, simply configuring both strong and weak ciphers does not inherently make a connection vulnerable to resource exhaustion; it primarily exposes the communication to cryptographic weaknesses.
When weak ciphers are employed, they are more susceptible to cryptanalysis, potentially allowing an attacker to decrypt, modify, or forge data without detection, thereby compromising the integrity of the transmitted information.
L2TP is a tunneling protocol, not a cipher suite, and a VPN concentrator would not revert to a different underlying protocol simply due to the configuration of different cipher strengths within its current protocol.
IPSec sequence numbers, typically 32-bit, are fixed parameters for anti-replay protection, and their bit-size is not altered by the strength of the cryptographic ciphers configured on a VPN concentrator.
Concept tested: Risks of weak cipher support, Downgrade attacks, Data integrity compromise
Source: https://learn.microsoft.com/en-us/windows-server/security/tls/tls-concepts?tabs=server#tls-downgrade-attack
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