A hooded man holds a laptop computer as cyber code is projected on him in this illustration picture taken on May 13, 2017. REUTERS/Kacper Pempel/Illustration

Dec 3 (Reuters) - Fintech firm Marquis is notifying U.S. banks and credit unions after an August ransomware attack allowed hackers to access files containing customer data, according to a company filing on Tuesday.

The Texas-based digital and physical marketing vendor detected suspicious activity on its network and later confirmed it had been hit by ransomware, the company said in a filing with Maine's attorney general.

An investigation found an intruder exploited Marquis' SonicWall firewall on August 14 and possibly acquired certain files from its systems, the filing shows.

Marquis said it is issuing notices on behalf of current and former business customers whose data it maintained. The review of accessed files found they contained personal information received from certain business customers.

Data potentially exposed include names, addresses, phone numbers, dates of birth, Social Security numbers, taxpayer identification numbers and some financial account information.

Marquis said it has not found evidence of misuse of the data, according to the disclosures.

(Reporting by Prakhar Srivastava in Bengaluru; Editing by Krishna Chandra Eluri)