Hallisey & D’Agostino, LLP Data Breach Exposes Personal Information of Over 16,000 Individuals
Hallisey & D’Agostino, LLP, a Connecticut-based public accounting firm, recently disclosed a data breach that compromised the sensitive personal information of 16,683 individuals across the U.S., including 74 in Maine. The firm, headquartered in Wethersfield, detected unusual activity in its network on October 21, 2025, prompting an immediate investigation with external cybersecurity experts.
The probe revealed that an unauthorized actor accessed the firm’s systems between September 28 and October 22, 2025, potentially exfiltrating files containing personal data. After a thorough review, completed on March 19, 2026, the firm confirmed the exposure and began notifying affected individuals via written notices on April 17, 2026.
The breach has drawn attention from Shamis & Gentile P.A., a class action law firm specializing in data breach cases, which is investigating potential legal action for those impacted. The incident underscores the ongoing risks of cyber threats targeting professional service providers handling sensitive client information.
Source: https://www.claimdepot.com/investigations/hallisey-dagost-data-breach-2026
Hallisey & D'Agostino, LLP cybersecurity rating report: https://www.rankiteo.com/company/hdllp
"id": "HDL1776537263",
"linkid": "hdllp",
"type": "Breach",
"date": "9/2025",
"severity": "85",
"impact": "4",
"explanation": "Attack with significant impact with customers data leaks"{'affected_entities': [{'customers_affected': '16683',
'industry': 'Accounting/Professional Services',
'location': 'Wethersfield, Connecticut, USA',
'name': 'Hallisey & D’Agostino, LLP',
'type': 'Public Accounting Firm'}],
'customer_advisories': 'Written notices sent to affected individuals',
'data_breach': {'data_exfiltration': 'Potential',
'number_of_records_exposed': '16683',
'personally_identifiable_information': 'Yes',
'sensitivity_of_data': 'High',
'type_of_data_compromised': 'Personal information'},
'date_detected': '2025-10-21',
'date_publicly_disclosed': '2026-04-17',
'description': 'Hallisey & D’Agostino, LLP, a Connecticut-based public '
'accounting firm, recently disclosed a data breach that '
'compromised the sensitive personal information of 16,683 '
'individuals across the U.S., including 74 in Maine. The firm '
'detected unusual activity in its network on October 21, 2025, '
'prompting an investigation with external cybersecurity '
'experts. The unauthorized actor accessed the firm’s systems '
'between September 28 and October 22, 2025, potentially '
'exfiltrating files containing personal data. The breach was '
'confirmed after a review completed on March 19, 2026, and '
'affected individuals were notified via written notices on '
'April 17, 2026.',
'impact': {'data_compromised': 'Sensitive personal information',
'identity_theft_risk': 'High',
'legal_liabilities': 'Potential legal action being investigated'},
'investigation_status': 'Completed',
'references': [{'source': 'Incident disclosure'}],
'regulatory_compliance': {'legal_actions': 'Class action investigation by '
'Shamis & Gentile P.A.'},
'response': {'communication_strategy': 'Written notices to affected '
'individuals',
'third_party_assistance': 'External cybersecurity experts'},
'title': 'Hallisey & D’Agostino, LLP Data Breach Exposes Personal Information '
'of Over 16,000 Individuals',
'type': 'Data Breach'}