The attackers have listed a number of data files on their site on the dark web, presumably taken while they were inside the Staircase systems, as proof of their attack.
As usual, NetWalker is another strain of malware that works only on systems running Microsoft's Windows operating system.
At the moment, Staircase has been given a little more than 12 days by the attackers before they make good on a threat to publish the actual data online.
Staircase offers advice on lending and debt restructuring, asset protection, insurance, property management and accounting.
There is no indication on the company's website of the revenue it pulls in annually, but from all appearances, it does not appear to be an overly large amount.
With this attack, NetWalker has now been used in 12 attacks this year that have been deemed worthy of being reported.
These include attacks on aircraft leasing asset manager SKY Leasing, tech repair specialists CSAT Solutions, Italian energy giant Enel, Indiana-based KYB Corporation, the biggest supplier of OEM automotive equipment to companies around the globe, data centre giant Equinix, US security software-as-a-service provider Cygilant, Australian workforce design and delivery firm Tandem Corp, and Jands, an Australian company that distributes some leading audio, lighting and staging brands for installation, production and retail industries throughout Australia and New Zealand.
Another attack of note was on Forsee Power, a company that designs and manufactures smart lithium-ion battery systems for electro-mobility markets, with a tenth being on Trinity Metro, a regional transportation authority of the state of Texas.
Prior to that the University of California in San Francisco admitted it paid US$1.14 million (A$1.56 million) to a gang that used NetWalker to attack its systems. A 12th case was that of Australian customer experience firm Stellar, that also operates across Asia, North America and Africa.