FEDERALItem 8.01 · voluntaryUnauthorized AccessFinancial ServicesFinanceData ExfiltratedCustomer Data InvolvedEmployee Data InvolvedPIIIdentity (basic)Government IDFinancial accountCredentialsHealth (basic)MediumActive

The Middlefield Banking Company

bd_d3345e13b9cb6e07 · schema v1 · pii pii-v1

Severity

Medium

Discovered

—

Filed

Dec 21, 2023

To disclose

—

Affected

Not disclosed

Linked

6 filings

Confidence

74%

Full breach record for The Middlefield Banking Company →2 incidents on file

Middlefield Banc Corp. disclosed via Item 8.01 8-K that its subsidiary, The Middlefield Banking Company, suffered a cyber-attack that disrupted computer systems. A forensic review determined that nonpublic information of current/former employees, customers and others was obtained, potentially including names, SSNs, driver's license info, dates of birth, financial account information, medical information, passport numbers, payment card info, and usernames/passwords. The Bank is notifying impacted individuals and offering complimentary identity protection services.

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Incident timeline — partial

? — ?

Breach window unknown

Dec 21, 2023

Filed

No interval is drawn: no breach start or discovery date is on record for this filing.

This filing is one of 6 filings about the same incident.View merged incident

Linked disclosures

Why this link?

Regulatory filings (5) · sorted by filing gap

Vermont State AGbd_2dee8d0f47f231bc2023-12-21Verified
Montana State AGbd_4752d46a27914d1a2023-12-21Candidate
New Hampshire State AGbd_719ea19c8e0056802023-12-21Verified
Massachusetts State AGbd_c1b3763023b7f8a72023-12-21Verified

Show 1 more filing ↓

California State AGbd_cc811a129570fcd52023-12-21Verified

Name: MIDDLEFIELD BANC CORP.
norm: middlefield banc
SEC CIK: 0000836147

Name: The Middlefield Banking Company
norm: the middlefield banking
Industry: Financial Servicesllm

Discovered: —
Materiality determined: —
Notification sent: —
Affected individuals: Not disclosed
Data types: PIIIdentity (basic)Government IDFinancial accountCredentialsHealth (basic)
Attack vector: Unauthorized Access
Threat actor: External
Regulator citations: Notifying regulatory authorities in accordance with applicable law

During the incident: Took immediate action to remediate the security vulnerability
Retained a cybersecurity firm to investigate the nature and scope of the incident
Notified law enforcement
Began notifying all potentially impacted individuals in accordance with applicable law
Notifying regulatory authorities in accordance with applicable law
Offering complimentary identity protection services to all potentially impacted individuals
Changes made: Remediated the security vulnerability
Source: Quoted from the filing itself, not independently verified.

Compliance flags: — (clock not assessable for this source)

Status: No extraction artifact recorded for this disclosure.

Filing propagation · 6 filings · 5 states

View merged incident ↗

Vermont State AGDec 21 · first

Montana State AGDec 21 · first

New Hampshire State AGDec 21 · first

Massachusetts State AGDec 21 · first

California State AGDec 21 · first

SEC 8-KDec 21 · first · this page

Evidence ladder

Leak-site claim

Attacker assertion only. Establishes: claim date, group, alleged victim.

Press / market report

Unlocks: incident narrative, operational impact. Still no compliance clock.

State AG / regulator filing

Unlocks: discovery date, data types, affected count, compliance clock.

SEC 8-K / victim statementThis record

Unlocks: materiality, stated response, full audit trail. Ceiling removed.

Source URL: https://www.sec.gov/Archives/edgar/data/836147/000119312523300259/d441183d8k.htm
DisclosureLens renders the full SEC/HHS filing inline below from the originating regulator’s public record (§4.5 fair report privilege).
Filed at: Dec 21, 2023
Raw hash: 0373eb19b3a0346fb4d5d6069608acd287a5202465ed65da2f35c3a37480b7da

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Linked disclosures

Regulatory filings (5) · sorted by filing gap

Reporting entityMIDDLEFIELD BANC CORP.

Victim entityThe Middlefield Banking Company

IncidentUnauthorized Access

Stated responseTook immediate action to remediate the security vulnerability

Complianceclock not assessable

Extraction provenanceno artifact recorded

Source provenancewww.sec.gov

Source filing