# Contact Chaining **Entity class:** Network-expansion method **Domain:** Intelligence analysis / communications metadata **Maturity:** Developed ## Definition **Contact chaining** expands from a seed identifier through direct and indirect contacts up to a defined hop limit. It can use telephone, email, account, or other metadata to construct a network neighborhood and community of interest. This is computationally similar to forward and backward [[wiki/Contact Tracing|contact tracing]], but the semantics differ. A communication edge is not biological exposure, ideological influence, or operational collaboration. Legal authority, selector validity, hop limits, minimization, and auditing determine scope. ## Relationships - **implemented by:** reported systems such as [[wiki/MAINWAY|MAINWAY]]. - **semantic enrichment:** [[wiki/Synapse|SYNAPSE]]. - **formal method:** [[wiki/Link Analysis|Link Analysis]] and [[wiki/Graph Analytics|Graph Analytics]]. - **risk:** exponential neighborhood growth and association by proximity. ## Sources / Provenance - [ACLU — NSA contact-chaining memo](https://www.aclu.org/documents/nsa-contact-chaining-memo) - [Wired — MAINWAY and precomputed contact chaining](https://www.wired.com/story/inside-the-nsas-secret-tool-for-mapping-your-social-network/)