Chaos ransomware gang claims attack on Optima Tax Relief, leaks 69 GB of stolen data

Optima Tax Relief, a prominent U.S. tax resolution firm, has become the latest victim of a cyberattack by the Chaos ransomware group, which claims to have stolen and leaked 69 gigabytes of sensitive company data.

The California-based firm, known for assisting individuals and businesses in resolving federal and state tax issues, was listed on Chaos ransomware’s data leak site earlier today. The cybercriminal group asserts that the stolen data includes a trove of internal corporate records as well as customer case files.

Given the nature of Optima’s services, such case files likely contain highly sensitive personal information, including Social Security numbers, addresses, and financial documentation, putting affected individuals at heightened risk for identity theft and other forms of exploitation.

Sources familiar with the incident have confirmed to BleepingComputer that the attack involved a double-extortion tactic. In addition to exfiltrating data, the attackers reportedly encrypted company servers, further disrupting operations and increasing pressure on the firm to meet ransom demands.

Chaos ransomware is a relatively new entrant in the cybercrime landscape, first surfacing in March 2025. Despite the similarity in name, this group is not affiliated with the Chaos ransomware builder, a tool used in earlier malware campaigns since 2021 to generate custom ransomware strains. The current Chaos operation has quickly gained notoriety, with Optima Tax Relief being among several organizations it has targeted. The gang has also claimed responsibility for an attack on the Salvation Army, though that organization has not publicly commented on the matter.

Optima Tax Relief, which markets itself as the nation’s leading tax resolution company and claims to have resolved over $3 billion in tax liabilities, has not yet issued a public statement regarding the breach. BleepingComputer reached out to the company for comment and is awaiting a response.