Enterprise Is the Target of 'Big Game Hunting'

GrandCrab has mutated, and enterprises should be worried.

A ransomware malware called GrandCrab has been active for the last year, but is now showing some changes in how it is spread. Researchers from Crowdstrike noted in a recent blogthat the newest version of it (5.2) is being rented as a service to affiliates who are sophisticated in "remote desktop protocol (RDP) and VNC (Virtual Network Computing) skills, and spammers who have experience in corporate networking."

These kinds of skills are needed to move into what has been called "big game hunting," which is targeted, low-volume/high-return ransomware deployments for enterprise installations. Crowdstrike says that the originating threat actor (whom they call PINCHY SPIDER) allows a limited number of accounts to rent the malware, and gives a 60-40 split in profits (60% to the customer). They also say that PINCHY SPIDER will negotiate up to a 70-30 split for "sophisticated" customers. The ads for affiliates on hacker forums are in the Russian language.

GrandCrab has a history of being thwarted by the cybersecurity community. A series of successful mitigations and decryptors have been developed by defenders as the malware morphs and changes methods. PINCHY SPIDER has retaliated by redeveloping the ransomware every time and even devised a zero-day exploit to aid in deployment. Crowdstrike observed that this new version of GrandCrab was involved in more sophisticated kinds of deployment than usually seen in ransomware attacks.

First looking around the victim installation, a threat actor affiliate was able to move laterally around the victim's network through the use of RDP and stolen credentials. In this effort, the affiliate used system administration tools such as Sysinternals Process Monitor, Process Hacker, and a file search tool called LAN Search Pro. They were able to end up deploying GrandCrab across several other hosts.

The push to spread over networks continued. In other attempts observed by Crowdstrike, control of the enterprise domain controller was obtained. Once this happened, the affiliate used the enterprise's own IT systems management software (LANDesk) to deploy the Phorpiex Downloader to hosts across the enterprise.

The downloader will spread itself to all the removable drives on the infected machines so as to further propagate itself throughout the network. Only then does it download and execute GrandCrab on the infected hosts.

How they charge for decrypting files is unusual compared to other ransomware efforts. PINCHY SPIDER encrypts individual hosts on the enterprise network and requests payment on a per-host basis, rather than a bulk payment for all the machines on a network.

As Crowdstrike puts it, "Running successful big game hunting operations results in a higher average profit per victim, allowing adversaries like PINCHY SPIDER and their partners to increase their criminal revenue quickly."

It seems ransomware is too profitable to disappear. Enterprises have to realize that their networks will come under new attacks as criminals find new ways to make their ill-gotten gains.

— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.

Editors' Choice
Tara Seals, Managing Editor, News, Dark Reading
Jim Broome, President & CTO, DirectDefense
Nate Nelson, Contributing Writer, Dark Reading