Attackers Use EternalBlue and PowerShell Scripts to Spread Cryptomining Malware Across Asia

A cryptomining malware campaign originally discovered in January is now using the EternalBlue exploit to target users in Asia, according to security researchers.

The investigation by Trend Micro showed the campaign involves several different approaches to infect machines and avoid detection while it mines Monero, most of which involve taking advantage of older applications and obfuscated PowerShell scripts.

In addition to EternalBlue — an exploit developed by the National Security Agency (NSA) that was linked to the widespread WannaCry and NotPetya ransomware attacks three years ago — the cryptomining malware also uses open-source tools, such as PowerDump, Invoke-SMBClient and Server Message Block (SMB) v1 protocol.

The campaign currently targets users based in Japan, Hong Kong, Taiwan, India and Vietnam, the researchers said.

How Miner Malware Uses Pass the Hash

Threat actors behind the attacks start by trying a list of commonly used passwords, such as “123456” and “welcome,” to break into a machine and gain network access. The campaign also makes use of a technique known as pass the hash in which attackers steal credentials stored in memory to connect to a remote server. Other options have included attacking targets with weak passwords using the Invoke-WMIMethod PowerShell script or EternalBlue for those with stronger passwords.

Once a machine has been infected and the media access control (MAC) address has been captured, the cybercriminals behind the cryptomining malware campaign try to get ahead of detection attempts by scanning for any antivirus products that may be in use.

Researchers also discovered five different components that have been used as part of the campaign, including a larger copy of the malware — essentially a dropped Trojan — that can get past sandboxes, as well as a binary executable compiled using Python and other PowerShell scripts. An open-source tool known as Invoke-ReflectivePEIInjection is used to drop the XMRig cryptominer onto the compromised machines using its own PowerShell process, rather than storing it as a file.

Keep Cryptomining Malware Off Servers, Too

While targeting individual machines with cryptomining malware is commonplace, the researchers noted that those behind this campaign were also trying to break into database servers by searching for those using weak SQL passwords.

This is similar to a recent investigation from IBM X-Force Incident Response and Intelligence Services (IRIS), which showed cryptojacking infections that took advantage of misconfigured servers in multinational corporations. Besides patching vulnerable systems and closing ports on external servers, IBM experts also recommend disabling legacy protocols such as SMB v1 and keeping a close eye on any data that leaks out through SMB ports.

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