Breach filing
ArchivedThompson Coburn LLP: 305,088 individuals, Nov 2024.
Thompson Coburn LLP reported a breach of unsecured protected health information to the HHS Office for Civil Rights on 4 November 2024. The filing records the organisation as a business associate in Missouri and lists 305,088 individuals affected, which makes it the 8th largest of the 164 Missouri filings on the register and the 67th largest of the 741 filings submitted nationally in 2024. Among the 13 Missouri filings made in 2024 it ranks 3rd.
Individuals affected
305,088
As reported to HHS
Modelled cost (IBM 2025)
$48.8M
Upper bound, method shown
Rank in MO
8th
of 164 Missouri filings
Rank in 2024
67th
of 741 filings nationally
Section F.1 / The filing
As posted by HHS OCR
Every value below is the portal's own field for this filing, plus its rank within the register.
- Covered entity type
- Business Associate
- Individuals affected
- 305,088
- Breach submission date
- 4 November 2024
- Submission year
- 2024
- Type of breach
- Hacking/IT Incident
- Location of breached information
- Network Server
- Business associate present
- Yes
- State
- Missouri (MO)
- Portal status
- listed in the HHS OCR breach portal archive
- Rank in Missouri by size
- 8th of 164
- Rank in 2024 nationally
- 67th of 741
- Missouri median filing
- 4,800 individuals
- Register id (derived)
- MO-20241104-thompson-coburn
Section F.2 / In context
Where this filing sits in Missouri and in 2024
OCR classifies the incident as a hacking or IT incident, with the breached information held in a network server. Hacking/IT Incident is the type recorded on 100 of the 164 Missouri filings (61%) and on 83% of all filings submitted in 2024. Network Server appears on 38% of Missouri filings.
A business associate is recorded as present on the filing, as it is on 23% of Missouri filings. At 305,088 individuals the breach is 64 times the Missouri median filing of 4,800 and 76 times the national median of 4,000 across all 7,884 filings. It is one of 801 filings of 100,000 or more individuals.
As of 28 August 2026 the case is listed in the HHS OCR breach portal archive. OCR's closing summary of the case is reproduced in full below.
Missouri's breach notification statute (Mo. Rev. Stat. 407.1500) requires notice to affected residents without unreasonable delay. Its attorney general threshold: more than 1,000 Missouri consumers. The HIPAA Breach Notification Rule ran alongside it: notice to affected individuals and to HHS without unreasonable delay and no later than 60 days after discovery, which is the clock that put this filing on the portal.
Multiplying 305,088 individuals by IBM's $160 customer-PII cost per record (Cost of a Data Breach 2025, the figure the site's calculator uses) gives a modelled $48.8M; the 2026 edition's $192 gives $58.6M. Both are modelled estimates with the method shown, not costs disclosed by Thompson Coburn LLP. Because the filing is above the roughly 100,000-record range in which the per-record figure is reliable, the result is an upper bound, not an estimate: fixed costs are spread across far more records at this scale.
Section F.3 / OCR closing summary
The portal's archived description, in full
Written by the Office for Civil Rights when the case was closed and reproduced verbatim from the HHS export.
Thompson Coburn LLP, the business associate (BA), reported that it experienced a ransomware attack affecting the electronic protected health information (ePHI) of 305,088 individuals. The ePHI involved included demographic, clinical, and financial information. The BA notified HHS, affected individuals, and the media. The BA took several corrective actions in response to the breach including improving its cybersecurity and providing additional HIPAA training to its workforce members.
Section F.5 / Modelled cost
305,088 individuals through IBM's per-record figures
Modelled cost / method shown, not a disclosed cost
Upper boundIBM 2025 customer PII, $160 per record
$48.8M
305,088 x $160
IBM 2026 customer PII, $192 per record
$58.6M
305,088 x $192
Method: individuals affected, as reported by Thompson Coburn LLP to HHS, multiplied by IBM's customer-PII cost per record (Cost of a Data Breach 2025 Figure 6 and the 2026 edition). No cost has been disclosed by the entity for this filing; the figure is a planning estimate, not a fact about the breach. IBM's per-record figures come from mid-volume breaches and IBM cautions against applying them to breaches involving millions of records; the site's per-record page explains where the multiplication holds and where it breaks down.
Context: IBM's average cost of a healthcare breach is $6.64M in the 2026 report ($7.42M in 2025); the global average across all sectors was $4.44M in 2025.
Cost per record: method and limits / Healthcare breach cost, IBM 2026
Section F.6 / Notification clock
Missouri statute and the HIPAA rule
State notification statute
Missouri: Mo. Rev. Stat. 407.1500
- Notice to individuals
- Without unreasonable delay
- Attorney general threshold
- More than 1,000 Missouri consumers (Without unreasonable delay)
- Private right of action
- No: AG has exclusive enforcement authority
- Penalty
- Up to $150,000 per breach (or series) for willful and knowing violations
The HIPAA Breach Notification Rule runs alongside the state statute: notice to affected individuals and to HHS without unreasonable delay and no later than 60 days after discovery.
Section F.7 / Peer filings
Missouri filings closest in size
Neighbours by size rank among Missouri filings in 2024, topped up from other years where 2024 has too few. Filings of 10,000 or more link to their own page.
| Covered entity | Type | Individuals | Submitted | Breach type | Location | BA |
|---|---|---|---|---|---|---|
| Ascension Health | Healthcare Provider | 5,466,931 | 3 Jul 2024 | |||
| North Kansas City Hospital | Healthcare Provider | 502,438 | 3 Jan 2024 | |||
| Liberty Hospital | Healthcare Provider | 264,541 | 8 Feb 2024 | |||
| Clay Platte Family MedicineOpen | Healthcare Provider | 53,916 | 18 Oct 2024 |
Index / Companion schedules
13 HHS breach register
→Hub: every filing, by state, year and entity.
04 Biggest breaches
→Mega-breaches with primary-source cost figures.
Industry / Healthcare
→IBM 2026: $6.64M average, 13 years at #1.
Regulation / HIPAA penalties
→OCR enforcement tiers and the 60-day rule.
11 50-state laws
→Deadline, AG threshold and penalties per state.
Cost / Per record
→Where the per-record model is reliable.
Provenance
Source: U.S. Department of Health and Human Services, Office for Civil Rights, Breach Portal (breaches affecting 500 or more individuals), retrieved 2026-08-28. Public domain. Individuals affected and dates as reported by the covered entity.
Portal: ocrportal.hhs.gov breach report. Statutory basis: HITECH Act section 13402(e)(4): the Secretary must post a list of breaches of unsecured protected health information affecting 500 or more individuals. Breaches affecting fewer than 500 individuals are reported to OCR annually and are not posted, so they are not on this register. Status wording follows the portal's two tabs ("Cases Currently Under Investigation" and "Archive") as of 28 August 2026; a filing moves to the archive when OCR closes the case. Modelled costs on this site are a method applied to the reported count, using IBM Cost of a Data Breach per-record figures, and are never a cost disclosed by the entity. This row: hhs-breach-archive__2026-08-28.csv, export row 681.
Corrections: if you represent a listed entity and the portal row has been amended, email [email protected] with the portal entry and we will re-pull the export.