DNS Sinkholing

Definition

DNS sinkholing is a defensive technique that redirects DNS queries for known malicious domains to a controlled IP address instead of the actual attacker-controlled server. By intercepting DNS resolution for command-and-control domains, malware distribution sites, and phishing infrastructure, sinkholing disrupts threat actor operations and provides visibility into compromised systems attempting to communicate with malicious infrastructure.

How It Works

DNS sinkholing is implemented on internal DNS resolvers or through DNS security services. Administrators configure the resolver to return a sinkhole IP address for domains identified as malicious through threat intelligence feeds, malware analysis, or incident response investigations. When a compromised system attempts to resolve a C2 domain, it receives the sinkhole IP instead of the attacker's server, preventing the malware from establishing communication. The sinkhole server logs all connection attempts, providing valuable intelligence about which internal systems are infected. Response Policy Zones (RPZ) provide a standardized mechanism for implementing DNS sinkholes with feeds from multiple threat intelligence providers. Sinkhole policies can be applied to entire domains, specific subdomains, or wildcard patterns. Organizations can run their own sinkhole servers or leverage cloud-based DNS security services that maintain continuously updated blocklists.

Why It Matters

Most malware relies on DNS resolution to locate its command-and-control infrastructure. By sinkholing known malicious domains, defenders can neutralize malware already present on the network without needing to immediately identify and remediate every infected endpoint. Sinkholing provides a network-wide containment capability that works against any device using the organization's DNS resolvers. The connection logs from sinkhole servers serve as a detection mechanism that identifies compromised systems requiring remediation.