An Iran-linked cyber-espionage group has been using new malware and data exfiltration techniques in recent attacks, security firm Nyotron has discovered.
The threat actor, known as OilRig, has been active since 2015, mainly targeting United States and Middle Eastern organizations in the financial and government industries. The group has been already observed using multiple tools and adopting new exploits fast, as well as switching to new Trojans in recent attacks.
Nyotron now says that OilRig has used roughly 20 different tools it its latest campaign, including off-the-shelf, dual-purpose utilities and previously unseen malware. In addition to data exfiltration, the group has been heavily focused on bypassing network-level security products to establish a foothold into targeted environments.
Since November 2017, the notorious Iran-linked threat group has been targeting various organizations in the Middle East with evolved tactics, techniques and procedures (TTPs), including the abuse of Google Drive and SmartFile for command and control (C&C) purposes, Nyotron’s report (PDF) reveals.
After compromising a targeted network (phishing emails are likely used to steal login credentials), the group downloads necessary tools from public file sharing services such as Dropbox, Degoo, Files.fm, and File.ac, and from an attacker-controlled server.
The hackers used Windows shares to transfer tools to endpoints that did not have an Internet connection or had downloads blocked by firewalls. They also used web shells to upload and execute files on compromised servers.
For the attacks, the hacker(s) built a sophisticated Remote Access Trojan (RAT) that uses Google Drive for C&C purposes and which is deployed on the target systems as a file named Service.exe. The malware registers as a service to achieve persistence, receives commands from the attacker’s account on Google Drive, and sends files to it.
With no anti-virus programs in VirusTotal detecting the RAT, multiple organizations appear to have been compromised by the malware. The account used to control the malware was created in August 2015, but wasn’t used until recently.
Another tool employed in this campaign is SmartFile.exe, which includes functionality supposedly taken from a GitHub repository, but with expanded capabilities. The tool uses SmartFile as C&C and can download and upload files to the file sharing service, in addition to executing received commands.
In addition to these tools, the attackers also leveraged a scheduled task running PowerShell scripts using AutoIt to gain persistence on the targeted systems. The analysed code, Nyotron says, is almost identical to the one used in an OilRig attack back in 2016.
The security researchers also discovered two main .aspx files the attackers used to gain persistence on Internet Information Services (IIS) Web servers. One of the files allowed the attackers to upload files to the system and was tailored to fit the folder paths of each server. A web shell was used to execute an arbitrary command on the infected machine using cmd.exe.
The OilRig hackers used a malicious IIS ISAPI filter as a covert way to execute commands on the compromised machine, and also deployed Myrtille onto infected machines (a tool that provides access to remote desktops and applications), but haven’t used the utility yet. Additionally, they deployed rpc.exe, a Meterpreter payload to gain persistence and support for various commands.
For privilege escalation on the compromised environments, the attackers mainly used variations of Mimikatz, but also attempted to use ProcDump to dump lsass.exe process memory.
For internal reconnaissance, the attackers used both legitimate and specially crafted tools, including Port Scanner (PS) to scan internal networks and external addresses, NBTScan to scan for open NETBIOS Name Servers on local or remote TCP/IP networks, and a tool to scan for EternalBlue exploitability (taken from a GitHub repository and converted to an executable using PyInstaller).
The attackers mainly used the EternalBlue exploit for lateral movement in the compromised networks. The exploits were likely taken from GitHub as well, and transformed from Python files into executables using PyInstaller. PsExec was also used to launch arbitrary commands on remote hosts in the network.
“State attackers and advanced hacking groups are continually finding new approaches to augment previous successful attacks. This latest OilRig evolution serves as a reminder that security leaders need to strengthen their endpoint protection using the defense in depth approach to safeguard against malware adopting next-generation tools and techniques,” Nir Gaist, founder and CTO of Nyotron, said.
Related: Iranian Hackers Use New Trojan in Recent Attacks
Related: Iranian Hackers Target IIS Web Servers With New Backdoor
Ionut Arghire is an international correspondent for SecurityWeek.
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