How does the Rogue System Sensor find rogue machines on the network?
Select the best answer; then select Submit.
A. The sensor listens to layer-4 broadcasts
B. The sensor listens passively to layer-2 broadcasts
C. You configure an Activity Scan to periodically scan the network
D. The sensor performs ARP/RARP requests
The Correct Answer and Explanation is:
The correct answer is:
B. The sensor listens passively to layer-2 broadcasts
Explanation:
A Rogue System Sensor (RSS) is a network security tool designed to detect unauthorized or unknown devices, known as rogue devices, on a network. These rogue machines can pose significant security threats, as they may introduce vulnerabilities or be used for malicious activities. The RSS works primarily by monitoring traffic on the network, often at layer-2 of the OSI model, to detect these devices.
Why Layer-2 Monitoring Works:
Layer-2, also known as the Data Link Layer, is responsible for the physical addressing of devices on a network. At this layer, devices use MAC (Media Access Control) addresses to communicate. Every device on a network sends broadcast messages, such as ARP (Address Resolution Protocol) requests, which help map IP addresses to MAC addresses. By listening to these layer-2 broadcasts, the RSS can identify devices based on their MAC addresses.
The RSS does this passively, meaning it does not actively send out probes or scans that could disrupt network operations. Instead, it monitors broadcast messages that are already being transmitted by devices on the network, such as ARP and DHCP requests. This is a highly efficient method, as it allows the RSS to detect new devices the moment they connect to the network and start communicating.
Other Answer Options:
- A. The sensor listens to layer-4 broadcasts: Layer-4 is the Transport Layer (e.g., TCP/UDP), and it handles end-to-end communication. Rogue detection typically doesn’t rely on layer-4 because this layer doesn’t deal with hardware-level identification like MAC addresses.
- C. You configure an Activity Scan: This suggests actively scanning the network, which is a more intrusive method compared to passive listening.
- D. The sensor performs ARP/RARP requests: While ARP is a layer-2 protocol, passive listening is more effective than actively sending requests, as sending ARP requests could raise suspicion on the network.
By passively listening to layer-2 broadcasts, the RSS can effectively detect rogue devices without causing network interruptions or alerting malicious actors.