Oracle WebLogic Server Flaw Exploited to Deliver Crypto-Miners

Threat actors are exploiting a recently patched vulnerability in Oracle WebLogic Server to infect systems with crypto-currency mining malware, FireEye reports. 

Identified as CVE-2017-10271, the vulnerability resides in the WebLogic Server Security Service (WLS Security) in Oracle WebLogic Server versions 12.2.1.2.0 and older, and was addressed by Oracle it its October 2017 Critical Patch Update (CPU).

After proof-of-concept code exploiting the bug was made public in December, activity associated with the exploitation of this vulnerability increased in volume, FireEye’s researchers say. Successful exploitation of the flaw on unpatched systems allows attackers to remotely execute arbitrary code. 

“We saw evidence of organizations located in various countries – including the United States, Australia, Hong Kong, United Kingdom, India, Malaysia, and Spain, as well as those from nearly every industry vertical – being impacted by this activity,” FireEye reported. 

The crypto-currency market boomed recently, and cybercriminals have not been shy in their attempts to take advantage of the market. However, actors involved in crypto-currency mining operations don’t normally target specific organizations, but rather launch attacks that are opportunistic in nature. 

Attackers abusing CVE-2017-10271 to infect targeted systems with crypto-miners used various tactics to achieve their purpose, the researchers discovered. Some of the incidents, for example, used PowerShell to drop the miner directly onto the victim’s system and leveraged ShellExecute() for execution. 

In other attacks, PowerShell scripts were used to deliver the miner, instead of downloading the executable directly. In addition to downloading the miner, the script would also attempt to achieve persistence through scheduled tasks. 

The script would delete the tasks created by other crypto-miners and would kill processes associated with those programs, in addition to being able to connect to mining pools with wallet key. It would also limit CPU usage to avoid suspicion. 

Tactics employed in other attacks also involved the use of tools such as Mimikatz and EternalBlue for lateral movement across Windows environments. 

The malware would first determine whether the system is 32-bit or 64-bit, to fetch a specific PowerShell script from the command and control (C&C) server. Next, it checks all network adapters and attempts to connect to every system in the network using extracted credentials, to run a PowerShell to drop and run the malware on the targeted system. 

The malware uses WMI (Windows Management Instrumentation) for persistence and can perform a Pass-the-Hash attack using NTLM information derived from Mimikatz, to download and execute the malware on remote machines. It sends the stolen credentials to a remote server using an HTTP GET request. 

If it fails moving laterally, the malware uses the PingCastle MS17-010 scanner to determine whether the target is vulnerable to EternalBlue. 

In scenarios targeting Linux machines, the vulnerability would be exploited to deliver shell scripts that include functionality similar to that of PowerShell scripts. They would attempt to kill already running crypto-miners and then download and execute the malware, in addition to creating a cron job to maintain persistence. 

“Use of cryptocurrency mining malware is a popular tactic leveraged by financially-motivated cyber criminals to make money from victims. We’ve observed one threat actor mining around 1 XMR/day, demonstrating the potential profitability and reason behind the recent rise in such attacks,” FireEye says. 

Although they might be seen as less risky when compared to ransomware operations, crypto-currency mining malware does pose a variety of risks. Systems infected with crypto-miners might experience slowed performance, but such operations could also be hiding additional malware. 

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