Trusted Relationship T1199
Tactic: Initial Access
Adversaries may breach or otherwise leverage organizations who have access to intended victims. Access through trusted third party relationship abuses an existing connection that may not be protected or receives less scrutiny than standard mechanisms of gaining access to a network.
Authoring guide
Patterns shared across the 18 rules above: which fields they filter on, what specific values they look for, and what they exclude. The catalog normalizes field names across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.
Fields filtered most (42 distinct)
The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.
Top indicator values (94 distinct)
Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique. Click a value to expand the rules under this technique that use it.
Exclusions (20 distinct)
Field/operator/value combinations excluded by rules under this technique (top-level not() clauses), sorted by how many rules exclude each. These are the false-positive paths the community has learned to filter out. A new rule that ignores the high-count entries here will likely fire on the same noisy paths. Click a value to expand the rules under this technique that exclude it.
Rules under this technique
Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.
Sigma 1 rule
Elastic 5 rules
- Entra ID Illicit Consent Grant via Registered Application
- Entra ID OAuth Authorization Code Grant for Unusual User, App, and Resource
- Entra ID OAuth Phishing via First-Party Microsoft Application
- New GitHub App Installed
- Okta Sign-In Events via Third-Party IdP
Kusto 6 rules
- Anomalous login followed by Teams action
- Azure Portal sign in from another Azure Tenant
- Dataverse - TI map IP to DataverseActivity
- External Upstream Source Added to Azure DevOps Feed
- Netskope - New Risky App Access vs 7-Day Baseline
- Netskope - Unsanctioned/Risky Cloud App Access (Shadow IT)