HackingFinancial ServicesHealthcareFinanceVulnerability ExploitCapture Stored DataCL0P Ransomware GangCl0pSupply Chain (3P Vendor)Data ExfiltratedData EncryptedRansom DemandedCustomer Data InvolvedMulti-Stage ChainHealth (basic)Identity (basic)Government IDPHIHighContained

MasTec, Inc. Care Opt Plus Group Benefits For Hourly & Salaried Employees Plan

bd_5de2718fda67da11 · schema v1 · pii pii-v1

Severity

High

Discovered

Jul 21, 2023

Filed

Nov 20, 2023

To disclose

17 weeks

Affected · nationwide

22,009675 in this filing

Confidence

68%

MasTec Care Opt Plus Plan notified WA AG of a third-party breach involving Delta Dental's MOVEit Transfer application. Unauthorized access occurred May 27-30, 2023, by CL0P ransomware gang. 22,009 individuals affected (675 in WA). Data included names, SSNs, DOBs, and health info. Notification sent Oct 27, 2023, with 24 months credit monitoring offered.

J jump to incidentP pin to compareR raw source

Washington clock✗ WA AG >90d17 weeks discovery → filing

Incident timeline

undetected · 55 days

discovery → filing · 17 weeks / 122 days

May 27, 2023

Begins

Jul 21, 2023

Discovered

Nov 20, 2023

Filed

vs. sector median

+9 wks slower

Tracked as a single-filing incident — the only disclosure on record for this event so far.Confirmed22,009 affectedView incident

Name: MasTec, Inc. Care Opt Plus Group Benefits For Hourly & Salaried Employees Plan
norm: mastec care opt plus group benefits
Domain: mastec.com

Name: MasTec, Inc. Care Opt Plus Group Benefits For Hourly & Salaried Employees Plan
norm: mastec care opt plus group benefits
Domain: mastec.com
Industry: Financial ServicesllmHealthcarellm

Discovered: Jul 21, 2023
Breach occurred: May 27, 2023 – May 30, 2023
Undetected for: 55 daysoccurrence → discovery
Materiality determined: —
Notification sent: Oct 27, 2023
Affected individuals: 22,009state + nationwide
Data types: Identity (basic)Government IDHealth (basic)
Data elements: NameSocial Security numberDate of birthHealth insurance ID
WA-stated cause: Unauthorized Access
WA-stated duration: lifecycle Unknowndexposure Unknownd
WA-stated discovery: Found after the fact
Attack vector: Third-Party / Supply Chain· CL0P Ransomware Gang
MITRE ATT&CK: T1190 Exploit Public-Facing ApplicationT1041 Exfiltration Over C2 ChannelT1486 Data Encrypted for Impact
Threat actor: CL0P Ransomware GangExternalFinancial
Regulator citations: Notified Washington Office of the Attorney General
Third party: via Delta Dental Plans Association
Initial access: exploit_public_facing

During the incident: Launched its own investigation
Retained outside advisors and cybersecurity experts
Began notifying known affected Washington residents via first class mail
Offered affected Washington residents 24 months of complementary IdentityWorks credit monitoring, identity restoration, and fraud detection services, through Experian
Changes made: Delta Dental implemented patches to the MOVEit file transfer application
Delta Dental took the affected application offline
Delta Dental updated systems to secure vulnerabilities and prevent further access
Source: Quoted from the filing itself, not independently verified.

Time to disclose: 17 weeks(122 days from discovery to filing)
Compliance flags: WA AG >90d
Discovery-date grounding: letter-groundedThe discovery date is the detection date narrated in the notification letter — the defensible tier.

Status: No extraction artifact recorded for this disclosure.

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 filingThis record

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

SEC 8-K / victim statement

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

Source URL: https://agportal-s3bucket.s3.amazonaws.com/databreach/BreachM15946.pdf
DisclosureLens links to the originating regulator URL — full filing bodies are not redistributed from public surfaces (§4.5).
Filed at: Nov 20, 2023
Raw hash: cf9cff0b51bee9a66db492247b8cca6b534a99664ebf853ddfb829ef8aa71738

Reporting entityMasTec, Inc. Care Opt Plus Group Benefits For Hourly & Salaried Employees Plan

Victim entityMasTec, Inc. Care Opt Plus Group Benefits For Hourly & Salaried Employees Plan

Incidentdiscovered Jul 21, 2023

Stated responseLaunched its own investigation

ComplianceWA AG >90d

Extraction provenanceno artifact recorded

Source provenanceagportal-s3bucket.s3.amazonaws.com