Marquis confirms sensitive personal data of 672,000 people stolen in ransomware attack

• Marquis confirms August 2025 breach impacted 670,000+ people
• Attack tied to SonicWall MySonicWall brute-force incident exposing firewall configs
• Marquis is suing SonicWall, which disputes connection between the two events

The August 2025 cyberattack on Marquis affected more than 670,000 people, the company confirmed earlier this week.

Marquis is a US fintech company building software for banks and credit unions, and to defend its internal network, it uses a firewall built by SonicWall.

In mid-September 2025, SonicWall warned its firewall customers to reset their passwords after unnamed threat actors brute-forced their way into the company’s MySonicWall cloud service.

Lawsuit filed

This tool allows SonicWall firewall users to back up their firewall configuration files, including network rules and access policies, VPN configurations, service credentials (LDAP, RADIUS, SNMP), or admin usernames and passwords (if stored in config).

SonicWall later confirmed that all of its customers were affected, and Marquis said it was among them.

Initially, there were no reports on the number of people affected. Marquis filed reports with multiple Attorney General’s Offices, stating that different types of information were stolen in different states. "The personal information potentially involved for Maine residents includes names, addresses, phone numbers, Social Security numbers, Taxpayer Identification Numbers, financial account information without security or access codes, and dates of birth,” it said in its Maine filing.

Now, BleepingComputer says the company confirmed more than 670,000 victims.

"The incident was limited to Marquis’s systems and did not affect our customer’s systems," the company told affected individuals, as per the publication. "Our customer reviewed the affected files on December 10, 2025, and afterwards worked to validate and identify individuals whose information may have been affected by the incident, and our customer worked as quickly as possible to obtain individuals’ most recent mailing address information."

In the meantime, Marquis has filed a lawsuit against SonicWall, claiming the attack was the result of the company’s conduct. SonicWall, on the other hand, argues that there is no evidence of the two incidents being connected.

Via BleepingComputer

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