Dynamic Host Configuration Protocol (DHCP) is a network protocol devices use to automatically obtain an IP address and other network configuration parameters from a DHCP server. For malware analysts, understanding how DHCP works is crucial for analyzing and tracking network malware behavior.
Here’s an explanation of how DHCP works from a malware analyst’s perspective:
- Discovery: When a device (e.g., a computer infected with malware) connects to a network, it sends a DHCP discovery request to locate a DHCP server. The request is broadcasted on the local network segment.
- Offer: DHCP servers on the network respond to the discovery request by offering a lease. The server sends a DHCP offer message, including an available IP address, subnet mask, default gateway, DNS server, and other configuration options.
- Request: The device selects one DHCP offer and sends a DHCP request message to confirm the lease. It includes the server’s IP address that offered the lease.
- Acknowledgment: The DHCP server responds with an acknowledgment message confirming the lease has been granted. It provides the device with the requested IP address and network configuration parameters.
From a malware analyst’s perspective, DHCP helps in malware analysis in the following ways:
- IP Address Identification: DHCP provides information about the IP address assigned to a device. By monitoring DHCP traffic, a malware analyst can identify malicious activity by looking for unusual or suspicious IP addresses associated with malware-infected devices.
- Network Enumeration: The DHCP lease may contain information about the default gateway, DNS servers, and other configuration options. Analyzing this information can help identify potential command-and-control servers or other network resources the malware uses.
- Tracking and Attribution: Active monitoring of DHCP transactions can help track the movement of infected devices across the network. This information can help attribute malware activity to specific devices and aid in incident response and mitigation efforts.
Overall, understanding how DHCP works allows malware analysts to gather valuable information about infected devices, track malicious activities on the network, and aid in mitigating malware threats.