Social EngineeringFinancial ServicesFinancePhishingStolen CredentialsData ExfiltratedCustomer Data InvolvedPIIIdentity (basic)Government IDFinancial accountMediumContained

THORNBURG INVESTMENT MANAGEMENT, INC.

bd_b2e15db64b4a5c15 · schema v1 · pii pii-v1

Severity

Medium

Discovered

Apr 13, 2021

Filed

Jan 7, 2022

To disclose

38 weeks

Affected

13state residents only

Linked

6 filings

Confidence

64%

Full breach record for THORNBURG INVESTMENT MANAGEMENT, INC. →

CorrectionPublished Oct 10, 2026

The Montana Department of Justice register lists this notice on 2021-01-07, before the breach it reports. The Massachusetts, Maine and Indiana registers list the same notice on 2022-01-07, so we publish 2022-01-07 as the date it was filed.

Read their full statement

Thornburg Investment Management, Inc. notified affected individuals of unauthorized access to employee email accounts between March 29 and April 30, 2021, following suspicious activity detected on April 13, 2021. The incident involved phishing leading to credential compromise and email collection. Impacted data included names and potentially SSNs and financial account numbers. Remediation included enhanced email security measures and Equifax credit monitoring services.

J jump to incidentP pin to compareR raw source

Incident timeline

undetected · 15 days

discovery → filing · 38 weeks / 269 days

Mar 29, 2021

Begins

Apr 13, 2021

Discovered

Jan 7, 2022

Filed

vs. sector median

+30 wks slower

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

Indiana State AGbd_69f5df6975be89742022-01-07Verified
Massachusetts State AGbd_a1ed418fcd6b26562022-01-07Verified
Maine State AGbd_e6d0b2bb474097362022-01-07Candidate
New Hampshire State AGbd_94c827c06515004b2022-01-12 · +5dVerified

Show 1 more filing ↓up to 27d gap

Maine State AGbd_ca2dc835fc9b5f492022-02-03 · +27dVerified

Name: THORNBURG INVESTMENT MANAGEMENT, INC.
norm: thornburg investment management

Name: THORNBURG INVESTMENT MANAGEMENT, INC.
norm: thornburg investment management
Industry: Financial Servicesllm

Discovered: Apr 13, 2021
Breach occurred: Mar 29, 2021 – Apr 30, 2021
Undetected for: 15 daysoccurrence → discovery
Materiality determined: —
Notification sent: —
Affected individuals: 13state-resident count only
Data types: PIIIdentity (basic)Government IDFinancial account
Attack vector: Phishing
MITRE ATT&CK: T1566.002 Spearphishing LinkT1078 Valid AccountsT1114 Email Collection
Threat actor: ExternalFinancial
Initial access: phishing_link

During the incident: Launched an internal investigation to determine the scope of the incident
Completed a review of the at-risk contents of the email accounts
Obtained addresses needed to provide notice to those potentially impacted
Put in place additional measures aimed to prevent a phishing attempt or compromise of our email systems in the future
Monitoring and identity restoration services through Equifax for a period of <<CM Length >> months
Changes made: Put in place additional measures aimed to prevent a phishing attempt or compromise of our email systems in the future
Source: Quoted from the filing itself, not independently verified.

Time to disclose: 38 weeks(269 days from discovery to filing)
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 ↗

Indiana State AGJan 7 · first

Massachusetts State AGJan 7 · first

Maine State AGJan 7 · first

Montana State AGJan 7 · first · this page

New Hampshire State AG+5d

Maine State AG+27d

Pattern: first filing Jan 7 (IN), last Feb 3 (ME) — a 27-day rolling notification. Rolling spreads often mean counsel is filing as thresholds trip per state. Why this link?

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://dojmt.gov/wp-content/uploads/OCP/Consumer-Notification-Letter-172.pdf
DisclosureLens links to the originating regulator URL — full filing bodies are not redistributed from public surfaces (§4.5).
Filed at: Jan 7, 2022
Raw hash: 8f125ee1b8faae7899367621dc7fd9573ce2be23ffc3b8ca859a207b4d8baeff

Linked disclosures

Regulatory filings (5) · sorted by filing gap

Reporting entityTHORNBURG INVESTMENT MANAGEMENT, INC.

Victim entityTHORNBURG INVESTMENT MANAGEMENT, INC.

Incidentdiscovered Apr 13, 2021

Stated responseLaunched an internal investigation to determine the scope of the incident

Complianceclock not assessable

Extraction provenanceno artifact recorded

Source provenancedojmt.gov