The correct answer is:
(b) VLAN circumvention
VLAN circumvention is a data-link layer vulnerability. It involves bypassing or misconfiguring VLANs (Virtual Local Area Networks) to gain unauthorized access to networks. Since VLANs operate at the data-link layer (Layer 2) of the OSI model, this is considered a vulnerability in the data-link layer.
Here’s why the other options are not correct for the data-link layer:
- (a) Physical Theft of Data: This is more of a physical security issue, not a data-link layer vulnerability.
- (c) Route spoofing: This involves manipulating routing tables, which is related to Layer 3 (Network layer) of the OSI model.
- (d) Weak or non-existent authentication: This can apply to many layers, but it's not specific to the data-link layer. It could be related to application, transport, or network layers depending on the context.
VLAN circumvention is the only option that specifically involves Layer 2 vulnerabilities.