One linked filing — more sources may join as they report · filed Apr 21, 2023. View entity profile → Other incidents for this victim →
incident inc_91aef13b81b64752 · merge_method deterministic
Discovered → first regulatory filing
Discovery to SEC materiality determination
FEDERAL
Materiality determination to SEC 8-K filing
Not recorded for this incident
Discovery variance · Leak precedence · Filing span — no leak-site claim in this cluster; needs two dated filings.
all SEC 8-K
Earliest sighting first · deep chronology in Litigation Timeline
Apr 12, 2023
Reported by SEC 8-K filing
Apr 12, 2023
Registrant determined the incident material — starts the SEC 4-business-day clock
Middlefield Banc Corp. reported a cyber-attack on April 12, 2023, disrupting systems at its subsidiary, The Middlefield Banking Company. The Bank remediated the vulnerability, engaged forensic investigators, and notified law enforcement. The investigation is ongoing to determine if customer data was impacted. No material financial impact is currently expected.
About this clustering
DisclosureLens links filings into incidents through layered matchers: deterministic rules (same source document, multistate filings of one breach, tight-window same-victim pairs), a weighted-similarity scorer for cross-source candidates, and an operator review queue for everything uncertain. Each link records its own method and confidence — shown per filing in the timeline below. The system defaults to NOT merging when uncertain, because a false merge (collapsing two unrelated breaches) is more harmful than a false split (showing related filings separately); uncertain pairs route to human review instead of auto-merging. Filing summaries shown in the timeline are AI-generated extracts — verify each against its linked source.