Definition
Blocking a reverse lookup based on the query's IP address value.
How it works
This technique prevents a client from learning domains deemed to be potentially malicious, which would have been delivered via reverse resolution responses over the DNS protocol.
Queries for reverse resolution requests (that is, requests where IP(s) are sent and a domain is returned) are collected, and the IP address(es) included in the query are examined. If the IP address(es) are in a range included in the blacklist, then the query is dropped.
Considerations
- The blacklist will have to be maintained and will need to be kept up to date with identified maintenance cycles to ensure lists are not stale.
- DNS query traffic can be transmitted over many different protocols, which presents a challenge to implementing methods to extract all DNS query IP address value(s).
- DNS has historically used UDP port 53, with TCP port 53 instead used for responses over 512 bytes or after a lack of response over UDP.
- Usage of new protocols to provide confidentiality for DNS traffic, such as DoH (DNS over HTTPS) and DoT (DNS over TLS), complicates collection of the IP address(es) in DNS queries. These protocols have often been enabled in browser settings transparently after a browser update, with DNS queries proxied over one of these cryptographic protocols through a specified host.
Implementation perspective
Reverse Resolution IP Denylisting should be treated as a technical defensive capability rather than a product checkbox. In practice, teams should define the protected scope, the conditions under which the technique acts, and the observable evidence that demonstrates the intended behavior. For this technique, likely engineering context includes Outbound Internet DNS Lookup Traffic.
Use the technique to create a logical or physical boundary that limits access, execution, communication, or movement.
Questions to ask
- What is being isolated, from whom or what, and under which conditions?
- Which flows or operations remain explicitly allowed across the boundary?
- What happens when the isolation mechanism fails or loses policy context?
- How is the boundary tested for alternate paths, bypasses, and unintended dependencies?
Evidence and validation
- Architecture and data-flow diagrams showing the isolation boundary
- Policy, rule, or configuration exports from enforcing components
- Tests of allowed, denied, and failure-state behavior
- Monitoring evidence for boundary violations and policy changes
Common failure patterns
- The intended boundary has undocumented alternate paths or inherited trust relationships.
- Rules accumulate without ownership, review, or removal of obsolete exceptions.
- Isolation is assumed from network location while application, identity, or management paths remain open.
This implementation perspective is original Bare Metal Cyber educational content. It does not replace the official D3FEND definition or establish that a specific product implements the technique.
Technique hierarchy
Top-level family
Parent techniques
Direct child techniques
None listed at this level.
Artifacts and ontology entities
These relationships describe how D3FEND connects a defensive technique to artifacts or other ontology entities. They describe graph semantics, not a product certification.
Explicit technique relationships
Show inferred artifact relationship paths (1)
Offensive-technique relationships
These relationships are generated from D3FEND graph paths and are explicitly experimental. They should be treated as hypotheses for defensive analysis—not as proof that the technique prevents, detects, or removes an offensive behavior.
ATT&CK Enterprise (2)
Authoritative sources
- Open this technique on the official D3FEND website ↗
- Open the official ontology resources ↗
- Use DNS Policy for Applying Filters on DNS Queries ↗Microsoft · UserManualReference
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