Low-profile Crysis ransomware suddenly stealing the show

Researchers have detected a sudden surge in attacks using Crysis ransomware, which encrypts virtually all file types, even those with no extension.
Researchers have detected a sudden surge in attacks using Crysis ransomware, which encrypts virtually all file types, even those with no extension.

Security experts have been watching and waiting for Locky and other high-profile ransomware families to expand their spheres of influence following the sudden demise of TeslaCrypt. But surprisingly, researchers at ESET have discovered that an under-the-radar ransomware known as Crysis has been silently and quickly gaining momentum, and is currently even more prevalent than Locky.

As ransomware goes, Crysis features some decidedly malicious traits. According to an ESET "We Live Security" blog post, Crysis encrypts virtually all file types – including those with no extension – on fixed, removable and network drives. “Most ransomware families are encrypting files with specific extensions, so this behavior is unusual,” said Ondrej Kubovic, EMEA security specialist, in an email interview with SCMagazine.com. “Also, various executable files (.exe, .dll) get encrypted which is not common in comparison to high-profile ransomwares.” As a result, the “affected computer may become unstable.”

On some Windows operating systems, Crysis can even run with administrator privileges, giving its encryption mechanism access to even more files.

As is usual with ransomware, victims must comply with given payment instructions in order to restore their computers' normal functionality. In this case, the attackers are typically seeking bitcoins worth between 400 and 900 euros, ESET has reported. The instructions are delivered via a text file that gets dropped into the affected computer's desktop folder.

First detected in February 2016, Crysis is reportedly spreading through a number of vectors. The most common one appears to be via widespread spam emails that use double file extensions that make executable files appear to be non-executable. Alternatively, the attackers are also “disguising malicious files as harmless-looking installers for various legitimate applications, which they have been distributing via various online locations and shared networks,” the ESET blog post states.

“We have seen the malware executable faking names of common applications such as: WinRar, MS_Excel, iExplore, setup2 [and] setap22,” said Kubovic to SCMagazine.com.

Beyond encryption, the trojan also collects the victim computer's name and some encrypted files and sends them to a remote command and control server.  It also sets certain registry entries so that it automatically executes any time the system is restarted. “By setting the registry entries, Crysis gains a stronger foothold in the system, making itself more difficult to remove,” said Kubovic.

In its blog post, ESET is advising readers that files encrypted by older variants of Crysis might be salvageable without paying the ransom, with the assistance of ESET technical support.

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