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CAPEC-668: Key Negotiation of Bluetooth Attack (KNOB)

Attack Pattern ID: 668
Abstraction: Standard
Status: Draft
Presentation Filter:
+ Description
An adversary can exploit a flaw in Bluetooth key negotiation allowing them to decrypt information sent between two devices communicating via Bluetooth. The adversary uses an Adversary in the Middle setup to modify packets sent between the two devices during the authentication process, specifically the entropy bits. Knowledge of the number of entropy bits will allow the attacker to easily decrypt information passing over the line of communication.
+ Likelihood Of Attack

Low

+ Typical Severity

High

+ Relationships
Section HelpThis table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
NatureTypeIDName
ChildOfMeta Attack PatternMeta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.115Authentication Bypass
CanFollowStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.20Encryption Brute Forcing
CanFollowMeta Attack PatternMeta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.94Adversary in the Middle (AiTM)
CanPrecedeMeta Attack PatternMeta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.148Content Spoofing
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Execution Flow
Explore
  1. Discovery: Using an established Person in the Middle setup, search for Bluetooth devices beginning the authentication process.

    Techniques
    Use packet capture tools.
Experiment
  1. Change the entropy bits: Upon recieving the initial key negotiation packet from the master, the adversary modifies the entropy bits requested to 1 to allow for easy decryption before it is forwarded.

Exploit
  1. Capture and decrypt data: Once the entropy of encryption is known, the adversary can capture data and then decrypt on their device.

+ Prerequisites
Person in the Middle network setup.
+ Skills Required
[Level: Medium]
Ability to modify packets.
+ Resources Required
Bluetooth adapter, packet capturing capabilities.
+ Consequences
Section HelpThis table specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
ScopeImpactLikelihood
Confidentiality
Read Data
Confidentiality
Access Control
Authorization
Bypass Protection Mechanism
Integrity
Modify Data
+ Mitigations
Newer Bluetooth firmwares ensure that the KNOB is not negotaited in plaintext. Update your device.
+ Example Instances
Given users Alice, Bob and Charlie (Charlie being the attacker), Alice and Bob begin to agree on an encryption key when connecting. While Alice sends a message to Bob that an encryption key with 16 bytes of entropy should be used, Charlie changes this to 1 and forwards the request to Bob and continues forwarding these packets until authentication is successful.
+ References
[REF-657] Jovi Umawing. "Bluetooth vulnerability can be exploited in Key Negotiation of Bluetooth (KNOB) attacks". MalwareBytes. 2019-08-21. <https://blog.malwarebytes.com/awareness/2019/08/bluetooth-vulnerability-can-be-exploited-in-key-negotiation-of-bluetooth-knob-attacks/>. URL validated: 2021-06-11.
+ Content History
Submissions
Submission DateSubmitterOrganization
2021-06-24CAPEC Content TeamThe MITRE Corporation
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Page Last Updated or Reviewed: June 24, 2021