MasTec Data Breach Exposes Sensitive Information of Over 25,000 Individuals
In October 2025, MasTec Inc., a leading U.S. infrastructure engineering and construction firm based in Coral Gables, Florida, detected unusual activity within a segment of its computer network. A subsequent investigation by third-party cybersecurity experts revealed that an unauthorized party had accessed part of the company’s systems for several days in August 2025.
After identifying the affected files, MasTec enlisted a data review firm to analyze the breach’s scope. The review concluded in February 2026, and notifications to impacted individuals began on May 11, 2026. The breach compromised the personal data of 25,220 people across the U.S., including 11 in Maine and 1,160 in South Carolina.
The ransomware group CL0P claimed responsibility for the attack on the dark web on October 29, 2025. While MasTec has not publicly disclosed the exact types of information exposed, potential data includes names, dates of birth, addresses, Social Security numbers, and financial details.
Legal firm Shamis & Gentile P.A. is investigating potential compensation claims for affected individuals. The incident underscores the ongoing risks to critical infrastructure providers and the delayed disclosure timelines in cybersecurity incidents.
Source: https://www.claimdepot.com/investigations/mastec-data-breach-2026
MasTec cybersecurity rating report: https://www.rankiteo.com/company/mas-tec
"id": "MAS1780936358",
"linkid": "mas-tec",
"type": "Ransomware",
"date": "5/2026",
"severity": "100",
"impact": "4",
"explanation": "Attack with significant impact with customers data leaks"{'affected_entities': [{'customers_affected': '25,220',
'industry': 'Infrastructure Engineering and '
'Construction',
'location': 'Coral Gables, Florida, U.S.',
'name': 'MasTec Inc.',
'type': 'Corporation'}],
'attack_vector': 'Ransomware',
'customer_advisories': 'Notifications sent to impacted individuals on May 11, '
'2026',
'data_breach': {'number_of_records_exposed': '25,220',
'personally_identifiable_information': 'Yes',
'sensitivity_of_data': 'High',
'type_of_data_compromised': ['Names',
'Dates of birth',
'Addresses',
'Social Security numbers',
'Financial details']},
'date_detected': '2025-10',
'date_publicly_disclosed': '2026-05-11',
'description': 'In October 2025, MasTec Inc. detected unusual activity within '
'a segment of its computer network. An investigation revealed '
'that an unauthorized party had accessed part of the company’s '
'systems for several days in August 2025. The breach '
'compromised the personal data of 25,220 people across the '
'U.S., including names, dates of birth, addresses, Social '
'Security numbers, and financial details. The ransomware group '
'CL0P claimed responsibility for the attack.',
'impact': {'data_compromised': 'Personal data of 25,220 individuals',
'identity_theft_risk': 'High',
'legal_liabilities': 'Potential compensation claims',
'payment_information_risk': 'High',
'systems_affected': 'Segment of computer network'},
'investigation_status': 'Concluded in February 2026',
'ransomware': {'ransomware_strain': 'CL0P'},
'references': [{'date_accessed': '2025-10-29',
'source': 'Dark web claim by CL0P'}],
'regulatory_compliance': {'legal_actions': 'Potential compensation claims by '
'Shamis & Gentile P.A.'},
'response': {'communication_strategy': 'Notifications to impacted individuals '
'beginning May 11, 2026',
'third_party_assistance': 'Cybersecurity experts and data review '
'firm'},
'threat_actor': 'CL0P',
'title': 'MasTec Data Breach Exposes Sensitive Information of Over 25,000 '
'Individuals',
'type': 'Data Breach'}