Definition
Analyzing failed connections in a network to detect unauthorized activity.
How it works
Connection Attempt Analysis in multiple ways.
Monitoring traffic to unallocated IP space
One approach looks for failed connection attempts against unallocated IP space. First, network traffic is captured to map out the network to identify network assets as well as unallocated IP space. The map is then used to determine if connection attempts are being made to the unallocated IP space.
Monitoring for sequentially transmitted traffic
Another approach passively inspects network traffic with application protocol analyzers observing network activity characteristics such as volume of packets sent/ received, TCP session attributes, and connection information between hosts (start time, source/destination host, services, etc.). Then using pattern matching to identify traffic which appears to be probing for network hosts.
Considerations
- Implementations that rely on analysis of unallocated IP address space increase in their complexity with network size and decentralized network infrastructure.
- Inventory of unallocated IP space should be continuously updated to mitigate the risk of false positives.
- IPv6 also introduces challenges including IPv6 traffic bypassing IPv4 specific protection systems (ex. firewalls and IDS) and complexity in managing both IPv6 and IPv4 addresses.
Implementation perspective
Connection Attempt Analysis 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 Intranet Network Traffic.
Use the technique to identify suspicious, unauthorized, or abnormal activity through observable evidence and repeatable analysis.
Questions to ask
- Which events, states, or artifacts must be observed for the analysis to work?
- What analytic logic, threshold, comparison, or signature turns observations into a finding?
- How are expected false positives, blind spots, and environmental variations documented?
- Who receives the result, and what action is expected when the technique produces a finding?
Evidence and validation
- Telemetry and data-source configuration records
- Analytic logic, thresholds, signatures, and version history
- Test cases demonstrating expected positive and negative results
- Alert, triage, escalation, and tuning records
Common failure patterns
- Required telemetry is missing, delayed, or transformed in a way that invalidates the analysis.
- The technique produces alerts without an accountable triage and response process.
- Detection coverage is claimed from product deployment without testing the relevant analytic behavior.
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 (15)
ATT&CK for ICS (3)
Authoritative sources
- Open this technique on the official D3FEND website ↗
- Open the official ontology resources ↗
- Detecting network reconnaissance by tracking intranet dark-net communications ↗VECTRA NETWORKS Inc · Nicolas BEAUCHESNE; Sungwook Yoon · PatentReference
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