Chinese UNC3886 Actors Exploiting VMware, Fortinet 0-days For Spying

In 2021, UNC3886, a suspected China nexus cyber espionage actor, was found to be targeting strategic organizations on a large scale, utilizing multiple vulnerabilities in FortiOS and VMware to install backdoors on the infected machines.

Fortinet and VMware have released patches to fix the vulnerabilities.

However, further investigations on the threat actor’s attack vector revealed the threat actor’s sophisticated, cautious, and evasive nature as they employed several layers of organized persistence over compromised machines.

This includes maintaining access to network devices, hypervisors, and virtual machines to gain alternative channel access.

Once they gained access to the compromised environment, they used publicly available rootkits for long-term persistence and also deployed malware to establish a connection with the C&C server.

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Further, they also extracted information from TACACS+ (Terminal Access Controller Access Control Server) authentication using custom malware.

Zero-Day Exploitation

According to the reports shared with Cyber Security News, the UNC3886 threat actor has been exploiting VMware vCenter vulnerability CVE-2023-34048 since 2021, which allows unauthenticated remote command execution on vulnerable vCenter machines.

Adding to this, there were several other vulnerabilities, such as:

• CVE-2022-41328 – Path Traversal – used to download and execute backdoors on FortiGate devices
• CVE-2022-22948 – Information Disclosure – Used to obtain encrypted credentials in vCenter’s postgresDB
• CVE-2023-20867 – Authentication Bypass – Used to execute unauthenticated Guest operations from compromised ESXi host
• CVE-2022-42475 – Heap-based Buffer Overflow – Used to execute unauthenticated arbitrary code or commands via specially crafted requests.

Further, several publicly available rootkits were used to establish long-term persistence. The rootkits used by UNC3886 are REPTILE, MEDUSA, and SEAELF.

REPTILE

This is an open-source linux rootkit that provides backdoor access to a system.

Additionally, this rootkit offered several functionalities, including actions like hiding files, processes, and network connections, the option to listen to specialized packets like TCP, UDP, or ICMP for activation, and an LKM launcher, which can be used to decrypt the actual kernel module code from the file and load it into memory.

Though this was an open-source rootkit, the threat actor made several code changes to customize it to their needs.

Most of the code changes were observed to be before version 2.1, introduced on March 1, 2020.

One of the important changes that was identified was inside the LKM launcher, which included a new function to daemonize a process.

MEDUSA And SEAELF

MEDUSA was another open-source rootkit that was implemented with dynamic linker hijacking via LD_PRELOAD.

The loader of MEDUSA was termed SEAELF. Two versions of MEDUSA were identified, both of which used XOR encryption keys to encrypt configuration strings.

Further, several additional changes were seen in the MEDUSA configuration, which can be used to create multiple MEDUSA artifacts.

Malware Usage

In addition to rootkits, the threat actor used several malware, such as MOPSLED and RIFLESPINE. MOPSLED is a shellcode-based modular backdoor that is capable of communicating over HTTP or a custom binary protocol over TCP to the C2. 

The main core functionality of this backdoor was its capability to retrieve plugins from the C2 server, and it also uses the ChaCha20 encryption algorithm.

Moreover, UNC3886 was found to be using a Linux variant of this backdoor to deploy on vCenter servers and on some compromised endpoints that already had REPTILE installed. 

RIFLESPINE is another cross-platform backdoor that uses Google Drive to transfer files and execute commands.

This backdoor uses CryptoPP library to implement the AES algorithm to encrypt the data transmitted between the compromised machine and the threat actor.

The deployment of this backdoor starts with creating an encrypted file on Google Drive with instructions to RIFLESPINE when getting executed on the compromised endpoint.

Further, the execution outputs will be encrypted, stored in a temporary file, and then uploaded to Google Drive again.

The instructions on the RIFLESPINE include the following:

• Download the file with the get command.
• Upload file with put command.
• Set the next call out time in milliseconds with settime.
• Execution of arbitrary commands with /bin/sh

Indicators Of Compromise

Filename	MD5	Family	Role
gl.py	381b7a2a6d581e3482c829bfb542a7de		UTILITY
install-20220615.py	876787f76867ecf654019bd19409c5b8		INSTALLER
lsuv2_nv.v01	827d8ae502e3a4d56e6c3a238ba855a7		ARCHIVE
payload1.v00	9ea86dccd5bbde47f8641b62a1eeff07		ARCHIVE
rdt	fcb742b507e3c074da5524d1a7c80f7f		ARCHIVE
sendPacket.py	129ba90886c5f5eb0c81d901ad10c622		UTILITY
sendPacket.py	0f76936e237bd87dfa2378106099a673		UTILITY
u.py	d18a5f1e8c321472a31c27f4985834a4		UTILITY
vmware_ntp.sh	4ddca39b05103aeb075ebb0e03522064		LAUNCHER
wp	0e43a0f747a60855209b311d727a20bf	GHOSTTOWN	UTILITY
aububbaditd	1d89b48548ea1ddf0337741ebdb89d92	LOOKOVER	SNIFFER
bubba_sniffer	ecb34a068eeb2548c0cbe2de00e53ed2	LOOKOVER	SNIFFER
ksbubba	89339821cdf6e9297000f3e6949f0404	MOPSLED.LINUX	BACKDOOR
ksbubba.service	c870ea6a598c12218e6ac36d791032b5	MOPSLED.LINUX	LAUNCHER
99-bubba.rules	1079d416e093ba40aa9e95a4c2a5b61f	REPTILE	LAUNCHER
admin	ed9be20fea9203f4c4557c66c5b9686c	REPTILE	BACKDOOR
authd	568074d60dd4759e963adc5fe9f15eb1	REPTILE	BACKDOOR
bubba	4d5e4f64a9b56067704a977ed89aa641	REPTILE	LAUNCHER
bubba_icmp	1b7aee68f384e252286559abc32e6dd1	REPTILE	BACKDOOR
bubba_loader	b754237c7b5e9461389a6d960156db1e	REPTILE	BACKDOOR
client	f41ad99b8a8c95e4132e850b3663cb40	REPTILE	BACKDOOR
dash	48f9bbdb670f89fce9c51ad433b4f200	REPTILE	LAUNCHER
listener	4fb72d580241f27945ec187855efd84a	REPTILE	BACKDOOR
packet	e2cdf2a3380d0197aa11ff98a34cc59e	REPTILE	CONTROLLER
authdd	fd3834d566a993c549a13a52d843a4e1	REPTILE.SHELL	BACKDOOR
authdd	4282de95cc54829d7ac275e436e33b78	REPTILE.SHELL	BACKDOOR
bubba_reverse	c9c00c627015bd78fda22fa28fd11cd7	REPTILE.SHELL	BACKDOOR
unknown	047ac6aebe0fe80f9f09c5c548233407	REPTILE.SHELL	BACKDOOR
usbubbaxd	bca2ccff0596a9f102550976750e2a89	RIFLESPINE	BACKDOOR
audit	3a8a60416b7b0e1aa5d17eefb0a45a16	TINYSHELL	CONTROLLER
lang_ext	6e248f5424810ea67212f1f2e4616aa5	TINYSHELL	BACKDOOR
sync	5d232b72378754f7a6433f93e6380737	TINYSHELL	CONTROLLER
x64	3c7316012cba3bbfa8a95d7277cda873	VIRTUALGATE	DROPPER
ndc4961	9c428a35d9fc1fdaf31af186ff6eec08	VIRTUALPEER	UTILITY
lsu_lsi_.v05	2716c60c28cf7f7568f55ac33313468b	VIRTUALPIE	ARCHIVE
vmsyslog.py	61ab3f6401d60ec36cd3ac980a8deb75	VIRTUALPIE	BACKDOOR
vmware_local.sh	bd6e38b6ff85ab02c1a4325e8af29ce4	VIRTUALPIE	LAUNCHER
cleanupStatefulHost.sh	9ef5266a9fdd25474227c3e33b8e6d77	VIRTUALPITA	LAUNCHER
client	a7cd7b61d13256f5478feb28ab34be72	VIRTUALPITA	BACKDOOR
duci	cd3e9e4df7e607f4fe83873b9d1142e3	VIRTUALPITA	BACKDOOR
payload1	62bed88bd426f91ddbbbcfcd8508ed6a	VIRTUALPITA	ARCHIVE
rdt	8e80b40b1298f022c7f3a96599806c43	VIRTUALPITA	BACKDOOR
rhttpproxy	c9f2476bf8db102fea7310abadeb9e01	VIRTUALPITA	BACKDOOR
rhttpproxy-IO	2c28ec2d541f555b2838099ca849f965	VIRTUALPITA	BACKDOOR
rpci	2bade2a5ec166d3a226761f78711ce2f	VIRTUALPITA	BACKDOOR
ssh	969d7f092ed05c72f27eef5f2c8158d6	VIRTUALPITA	BACKDOOR
nds4961l.so	084132b20ed65b2930129b156b99f5b3	VIRTUALSHINE	BACKDOOR

Network-Based Indicators

IPv4	ASN	Netblock
8.222.218.20	45102	Alibaba
8.222.216.144	45102	Alibaba
8.219.131.77	45102	Alibaba
8.219.0.112	45102	Alibaba
8.210.75.218	45102	Alibaba
8.210.103.134	45102	Alibaba
47.252.54.82	45102	Alibaba
47.251.46.35	45102	Alibaba
47.246.68.13	45102	Alibaba
47.243.116.155	45102	Alibaba
47.241.56.157	45102	Alibaba
45.77.106.183	20473	Choopa, LLC
45.32.252.98	20473	Choopa, LLC
207.246.64.38	20473	Choopa, LLC
149.28.122.119	20473	Choopa, LLC
155.138.161.47	20473	Gigabit Hosting Sdn Bhd
154.216.2.149	55720	Gigabit Hosting Sdn Bhd
103.232.86.217	55720	Gigabit Hosting Sdn Bhd
103.232.86.210	55720	Gigabit Hosting Sdn Bhd
103.232.86.209	55720	Gigabit Hosting Sdn Bhd
58.64.204.165	17444	HKBN Enterprise Solutions Limited
58.64.204.142	17444	HKBN Enterprise Solutions Limited
58.64.204.139	17444	HKBN Enterprise Solutions Limited
165.154.7.145	135377	Ucloud Information Technology Hk Limited
165.154.135.108	135377	Ucloud Information Technology Hk Limited
165.154.134.40	135377	Ucloud Information Technology Hk Limited
152.32.231.251	135377	Ucloud Information Technology Hk Limited
152.32.205.208	135377	Ucloud Information Technology Hk Limited
152.32.144.15	135377	Ucloud Information Technology Hk Limited
152.32.129.162	135377	Ucloud Information Technology Hk Limited
123.58.207.86	135377	Ucloud Information Technology Hk Limited
123.58.196.34	135377	Ucloud Information Technology Hk Limited
118.193.63.40	135377	Ucloud Information Technology Hk Limited
118.193.61.71	135377	Ucloud Information Technology Hk Limited
118.193.61.178	135377	Ucloud Information Technology Hk Limited

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