- Marquis confirms that the August 2025 breach affected 670,000+ people
- Attack linked to SonicWall MySonicWall brute-force incident exposing firewall configurations
- Marquis is suing SonicWall, which disputes the connection between the two events
The August 2025 Marquis cyberattack affected more than 670,000 people, the company confirmed earlier this week.
Marquis is an American fintech company that builds 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.
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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 administrator usernames and passwords (if stored in configuration).
SonicWall later confirmed that all of its customers were affected, and Marquis said it was among them.
Initially, there were no reports of the number of people affected. Marquis filed reports with several 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, telephone numbers, social security numbers, taxpayer identification numbers, financial account information without security or passwords, and dates of birth,” it said in its Maine filing.
Now, Bleeping Computer says the company confirmed more than 670,000 victims.
“The incident was limited to Marquis’ systems and did not affect our customers’ systems,” the company told affected individuals, according to the publication. “Our client reviewed the affected files on December 10, 2025 and subsequently worked to validate and identify individuals whose information may have been affected by the incident, and our client worked as quickly as possible to obtain individuals’ most recent mailing address information.”
Meanwhile, Marquis has filed a lawsuit against SonicWall, claiming the attack was the result of the company’s conduct. SonicWall, on the other hand, claims that there is no evidence that the two incidents are connected.
Via Bleeping Computer
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