New Sardonic Backdoor from FIN8 Threat Actor

Attack Flow
The attackers began with network reconnaissance, obtaining information about the domain (users, domain controllers) and continued with lateral movement and privilege escalation. In addition to the use of WMIExec, SMBExec from the same toolset (Impacket), along with, of course, the offensive features of their signature backdoor, BADHATCH.
The BADHATCH loader was deployed using PowerShell scripts downloaded from the 104.168.237[.]21 IP address
using the legitimate sslip.io service. It was used during the reconnaissance, lateral movement, privilege escalation
and possibly impact stages.
There were multiple attempts to deploy the Sardonic backdoor on domain controllers in order to continue with
privilege escalation and lateral movement, but the malicious command lines were blocked.

Persistence
Deployment of this backdoor begins by running the Sardonic loader. First, a PowerShell script named “sldr.ps1” (SHA256 edfd3ae4def3ddffb37bad3424eb73c17e156ba5f63fd1d651df2f5b8e34a6c7) is copied to the victim machine and executed.
This was performed manually by the attackers, rather than being installed at one point as part of an automated loader process.
This script contains two base-64 strings, corresponding to two additional PowerShell scripts: the first is an RC4-encrypted second stage, and the second one implements the decryption algorithm for the former.
In an improvement from earlier loaders used by FIN8, the decryption key “B4a0f3AE251b7689CFdDe1” is not included in the sample, but is given as a command-line argument.

.NET loader and downloader shellcode
This stage consists of a .NET assembly that contains a piece of shellcode, compressed using GZip and RC4-encrypted, using the key “CA0ac8F6655244d2E10e7819BD337bf9”, which is contained in the binary.
Since the shellcode is both self-modifying and contains a self-inject feature, an unmodified copy of itself is required.
It is prepended by a null-terminated “4BMARC2WKL” marker and copied in the same buffer, immediately before the
copy that is executed.
The second copy of the shellcode is executed from the beginning, using the Marshal.GetDelegateForFunctionPointer method.

Sardonic backdoor
The Sardonic backdoor is written in C++ and has the same C&C servers as the downloader shellcode (“api-cdn[.]net”, “git-api[.]com”, “api-cdnw5[.]net”), and talks over port 443 as well.
It can obtain information about the system, execute commands, and has a plugin system that can load specially made DLLs and execute their functions.
Research groups believe that more than one person developed this project, as there are some differences in code style and level of use of the C++ standard library between functions.

Sign Up For Threat Alerts

Loading...
Threats Icon

Aug 14, 2022

US Cert Alert – Zeppelin Ransomware

The Federal Bureau of Investigation (FBI) and the Cybersecurity and Infrastructure Security Agency (CISA) are...

Threats Icon

Aug 11, 2022

Cisco Talos shares insights related to recent...

Initial access to the Cisco VPN was achieved via the successful compromise of a Cisco...

Threats Icon

Aug 11, 2022

Andariel deploys DTrack and Maui ransomware

The CISA published an alert, entitled, "North Korean State-Sponsored Cyber Actors Use Maui Ransomware To...

Threats Icon

Aug 09, 2022

Albanian Government Organizations Targeted By Possible Iranian...

Mandiant identified the ROADSWEEP ransomware family and a Telegram persona which targeted the Albanian government...

Threats Icon

Aug 08, 2022

BumbleBee Roasts Its Way to Domain Admin

Threat actors used BumbleBee as the initial access vector. BumbleBee is a malware loader that...

Threats Icon

Aug 08, 2022

RapperBot – new evolving malware

FortiGuard Labs has been tracking a rapidly evolving IoT malware family known as "RapperBot". This...

Threats Icon

Aug 04, 2022

Google Drive And Dropbox Used By APT29...

Cloaked Ursa (aka: APT29) has been targeting governmental entities in several countries with spear-phishing campaigns...

Threats Icon

Aug 03, 2022

Manjusaka: A Chinese sibling of Sliver and...

Cisco Talos recently discovered a new attack framework called "Manjusaka" being used in the wild...

Threats Icon

Aug 03, 2022

macOS Targeted With The CloudMensis Multi-Staged Malware

ESET researchers discovered a previously unknown macOS backdoor that spies on users of the compromised...

Threats Icon

Aug 01, 2022

Attackers Target Ukraine With GoMet Backdoor

Since the Russian invasion of Ukraine began, Ukrainians have been under a nearly constant barrage...

Threats Icon

Jul 31, 2022

Untangling KNOTWEED: European private-sector offensive actor using...

The Microsoft Threat Intelligence Center (MSTIC) and the Microsoft Security Response Center (MSRC) found a...

Threats Icon

Jul 31, 2022

Untangling KNOTWEED: European private-sector offensive actor using...

The Microsoft Threat Intelligence Center (MSTIC) and the Microsoft Security Response Center (MSRC) found a...

Threats Icon

Jul 26, 2022

EvilNum Targets Cryptocurrency, Forex, Commodities

Proofpoint Threat Research observed the group Proofpoint calls TA4563 targeting various European financial and investment...

Threats Icon

Jul 25, 2022

Lightning Framework: New Undetected “Swiss Army Knife”...

Lightning is a previously undocumented and undetected Linux threat. Lightning is a modular framework we...

Threats Icon

Jul 24, 2022

Redeemer Ransomware

Redeemer 2.0 Being Distributed Via Affiliate Program Cyble Research Labs has constantly been tracking emerging...