A new Uiwix ransomware variant has been detected using EternalBlue to gain access to vulnerable systems. Businesses that have not yet patched they systems are vulnerable to this new attack.

In contrast to the WannaCry ransomware variant that was used in Friday’s massive ransomware campaign, Uiwix ransomware is a fileless form of ransomware that operates in the memory. Fileless ransomware is more difficult to detect as no files are written to the hard drive, which causes problems for many antivirus systems. Uiwix ransomware is also stealthy and will immediately exit if it has been installed in a sandbox or virtual machine.

Trend Micro reports that the new Uiwix ransomware variant also “appears to have routines capable of gathering the infected system’s browser login, File Transfer Protocol (FTP), email, and messenger credentials.”

As with WannaCry ransomware, the ransomware is not being spread via email. Instead the attackers are searching for vulnerable systems and are taking advantage of SMB vulnerabilities and attacking computers over TCP port 445. Infection with Uiwix sees the Uiwix extension added to encrypted files. The ransom demand to supply keys to decrypt locked files is $200.

The threat does not appear to be as severe as WannaCry, as the attackers are manually targeting vulnerable systems. Crucially, the ransomware lacks the wormlike properties of WannaCry. If one machine is infected, the ransomware will not then spread to other networked devices.

Since the WannaCry attacks, many businesses have now implemented the MS17-010 patch and have blocked EternalBlue attacks. Microsoft has also released a patch for Windows XP, Windows Server 2003, and Windows 8, allowing users of older, unsupported Windows versions to secure their systems and prevent attacks.

However, the search engine Shodan shows there are still approximately 400,000 computers that have not yet been patched and are still vulnerable to cyberattacks using the EternalBlue exploit.

Another threat that uses the EternalBlue and DoublePulsar exploits is Adylkuzz; however, the malware does not encrypt data on infected systems. The malware is a cryptocurrency miner than uses the resources of the infected computer to mine the Monero cryptocurrency. Infection is likely to see systems slowed, rather than files encrypted and data stolen.

Other malware and ransomware variants are likely to be released that take advantage of the exploits released by Shadow Brokers. The advice to all businesses is to ensure that software is patched promptly and any outdated operating systems are upgraded. Microsoft has issued a patch for the older unsupported systems in response to the WannaCry attacks, but patches for Windows Server 2003, Windows XP and Windows 8 are unlikely to become a regular response to new threats.