APT Cloud Atlas: Unbroken Threat

Introduction

Specialists at the PT Expert Security Center have been monitoring the Cloud Atlas group since May 2019. According to our data, its attacks have been targeting the government sector of the following countries:

Russia
Belarus
Azerbaijan
Turkey
Slovenia

The goals of the group are espionage and theft of confidential information.

The group typically uses phishing emails with malicious attachments as the initial vector for their attacks.

In the third quarter of 2022, during our investigation we identified a phishing campaign targeting employees of Russian government agencies. The attackers used targeted mailing based on the professional field of the recipients, even though we found no publicly available information about them.

We first knew about the attackers back in 2014, when Kaspersky researchers published a report. Since then, their tools have not changed much (you can find more about them in the "Malware analysis" section). However, there has not yet been a detailed analysis and description of the functionality of these tools.

In this report, we'll discuss the main techniques of the Cloud Atlas group, and take an in-depth look at the tools they use.

Analysis of the documents found

As in previous years, the group begins its attack by sending phishing emails, using current geopolitical issues that are directly related to the target country as a bait text. An example of an email with malicious content that was sent as part of the campaign in 2022 is shown in Figure 1. Pay special attention to the sender's address: the attackers disguised themselves as the news portal Lenta.ru, well-known in Russia and the CIS. However, email addresses with such a domain can be created with Rambler (Figure 2).

APT Cloud Atlas: Unbroken Threat — Figure 11. The contents of the HTA file

An examination of the document and its contents revealed that a vulnerability in Equation Editor was used to launch the exploit payload. The shellcode (highlighted in red in Figure 12) is located inside one of the document's objects and is executed in the context of the EQNEDT32.EXE process.

The direct link to the HTA file (through which the loading is performed) is stored in the body of the shellcode (Figure 14) and is additionally XOR-encrypted with the one-byte value of 0x12.

As seen in Figure 11, the HTA file is designed to create on the disk the VBS scripts with the payload for subsequent stages, as well as an LNK file with the main payload containing the code for loading binary modules. Thus, the main task of the VBS macros (in our case, both macros had similar names: unbroken.vbs and unbroken.vbs.vbs) is to deobfuscate the contents of the LNK file (shown in Figure 15) and transfer control to it, after which the payload which was downloaded by the LNK file code is launched (we will discuss this in the "Malware analysis" section).

It is also worth noting that malicious documents which exploit the same vulnerabilities in Equation Editor and contain identical object names (for example, "weaseoijsd",highlighted in red in Figure 16) in RTF documents were analyzed by Cisco Talos Intelligence specialists and attributed to the Bitter APT group.

The second chain that we found is downloading malicious PowerShell scripts via remote templates (Figure 17), which in turn download malicious components (mostly Base64-encoded).

We also encountered cases of an intermediate .NET loader that downloaded a payload from a remote server and transferred control to it.

This .NET loader is decoded from Base64 and launched by a PowerShell script (Figure 18).

The export (Figure 19), activated from the loader, takes all the necessary parameters for network communication, including the connection encryption key (highlighted in yellow in Figure 18).

The communication is encrypted with a simple XOR operation with the transferred key (Figure 20).

We also noted that almost all of the functions that decrypt the loader contain a large amount of polymorphic code. This performs various operations with strings located inside the image, stack strings, as well as with their individual elements (Figure 22 shows an example). However, these operations do not have any effect on the decrypted data itself. They are used to calculate various variables and constants that affect the decryption parameters (data size, offsets, and so on), as well as to complicate the analysis process. The decrypted data is copied to a pre-allocated memory area as a valid PE image, after which control is transferred to it.

Main loader

The loader, in turn, is responsible for reading the data from the file containing the main payload, as well as for its decryption and unpacking.

First, the loader decrypts the configuration located in its body. The decryption algorithm (Figure 23) is single-byte XOR with an embedded key. After decryption, the configuration is validated.

We noted that the configuration has not changed since previous studies—it contains the same data and parameters (Figure 23).

Analyzing this function allowed us to understand that in this case the communication scheme is identical to the one described above: data is transferred by function calls from the table of virtual methods of the same COM object (in this case, PUT is used as the communication method).

Other than this, the analysis of the loaded module reveals nothing of interest. It simply performs a recursive search in the directories of certain paths.

It's worth noting that for each type of disk connected to the computer, a different type of search is used (Figure 36). It is also possible to steal files from remote servers—in this case, usernames and passwords (stored in the malware configuration) are transferred as parameters.

Let's also have a look at the function responsible for analyzing the contents of the scanned directories (Figure 37). It's worth noting that the function itself does not read the file directly. Instead, the pointer to the read function (pfnReadFile in the figure) is transferred through the global context—the structure that is initialized at the initial stage of the application—and the function is called this way.

Network infrastructure

All the domains that we discovered in the 2019–2021 attacks were registered through the anonymous registrar bitdomain[.]biz. This resource guarantees complete anonymity and payment on the service is made exclusively in bitcoins.

After analyzing the SOA records of the domains, we found that the admin email address field contains perfectly normal email addresses. In some cases, they turned out to be the registrant addresses that we found in WHOIS. Therefore, in those domains where WHOIS was hidden by the privacy settings, it can be assumed that the email in the SOA is the email of the registrant.

Domain	email
mynewtemplate.com	[email protected]
new-template.com	[email protected]
upgrade-office.com	[email protected]
upgrade-office.org	[email protected]
msofficeupdate.org	[email protected]
officeupgrade.org	[email protected]
newoffice-template.com	[email protected]
template-new.com	[email protected]

When analyzing the 2022 campaign, we found a pattern: all the control servers registered by the attackers are used only to load remote templates.

List of the detected servers:

checklicensekey.com
comparelicense.com
driver-updated.com
sync-firewall.com
system-logs.com
technology-requests.net
translate-news.net

We also discovered an interesting fact: the attackers disguised one of the control servers (technology-requests.net), trying to make it look like the site https://www.hoosierheightsindianapolis.com (Figure 38).

Figure 39 shows what the malicious site looked like on July 26, according to webcache.googleusercontent.com.

The malicious tools communicate through a cloud service (similar to previous years), namely OpenDrive (https://www.opendrive.com). The service is used for both storing the malware modules to be loaded and for loading the collected data. In this case, a temporary mailbox is used for logins.

Conclusion

The Cloud Atlas group has been active for many years, carefully thinking through every aspect of their attacks. The group's toolkit has not changed for years—they try to hide their malware from researchers by using one-time payload requests and validating them. The group avoids network and file attack detection tools by using legitimate cloud storage and well-documented software features, in particular in Microsoft Office.

The attackers also carefully choose their victims and target their attacks: the group used targeted mailings based on the professional field of the recipients, but we noted the absence of any publicly available information about the recipients, which could indicate a well-prepared attack.

We predict that the group will continue to operate, increasing the complexity of its tools and attack techniques due to the fact that it has once again attracted the attention of researchers.

Authors: Denis Kuvshinov, Aleksandr Grigorian, Daniil Koloskov, Positive Technologies

The article's authors thank the incident response and threat intelligence teams PT Expert Security Center for their help in drafting the story.

Detection of CloudAtlas group activity by Positive Technologies products

MP SIEM

The following correlation rules analyze triggered processes and help identify the described activity:

Suspicious_Connection
Malicious_Office_Document
Windows_Autorun_Modification

The following correlation rules analyze the triggered scripts and help detect the described activity:

Execute_Malicious_Powershell_Cmdlet
Execute_Malicious_Command

Implementation of D3FEND techniques in MP SIEM, which will help in detecting CloudAtlas grouping activity

D3FEND ID

Name of technique D3FEND

Description

D3-PA

Process Analysis

CloudAtlas group activity can be identified through the rules of process analysis.

D3-SEA

Script Execution Analysis

CloudAtlas group activity can be detected through the analysis rules of the launched scripts.

PT NAD

PT NAD contains a CloudAtlas reputation list, which will help in identifying CloudAtlas grouping activity.

Implementation of D3FEND techniques in PT NAD, which will help in detecting CloudAtlas activity.

D3FEND ID

Name of technique D3FEND

Description

D3-DNSTA

DNS Traffic Analysis

Using reputation lists to detect Cloud Atlas group activity

D3-FC

File Carving

Extracting from traffic the files downloaded by the Cloud Atlas group

PT Sandbox

PT Sandbox verdicts on CloudAtlas grouping activity:

Trojan.Win32.Generic.a
Trojan.Win32.RegLOLBins.a
Backdoor.Win32.CloudAtlas.a
Trojan-Downloader.Win32.Generic.a

Network traffic analysis rules to help detect CloudAtlas grouping activity:

LOADER [PTsecurity] Possible CloudAtlas
SUSPICIOUS [PTsecurity] PROPFIND method in http request
SUSPICIOUS [PTsecurity] MKCOL method in http request

Yara-rules, which will help in detecting CloudAtlas grouping activity:

PTESC_tool_win_ZZ_OfficeTemplate__Downloader__DOC
PTESC_exploit_win_ZZ_MalDoc__CVE201711882__Rtf__CA

Implementation of D3FEND techniques in PT Sandbox, which will help in detecting CloudAtlas grouping activity

D3FEND ID	Name of technique D3FEND	Description
D3-PA	Process Analysis	Analysis of the behavior of processes created by malicious applications of the Cloud Atlas group
D3-FA	File Analysis	Analysis of Cloud Atlas group files to determine their status and functionality
D3-NTA	Network Traffic Analysis	CloudAtlas activity can be detected through traffic analysis

Yara

rule PTESC_tool_win_ZZ_OfficeTemplate__Downloader__DOC { strings: $a = {00 A5 06 6E 04 B4} $b = {FF FF FF 7F FF FF FF 7F} $c = {B4 00 B4 00 81 81 12 30 00} $pref_1 = {68 00 74 00 74 00 70 00 3A 00 2F 00 2F} $pref_2 = {68 00 74 00 74 00 70 00 73 00 3A 00 2F 00 2F} condition: uint16be ( 0 ) == 0xd0cf and ( for any i in ( 300 .. 400 ) : ( uint8be ( @a + i ) == 0x68 and uint8be ( @a + i + 2 ) == 0x74 and uint8be ( @a + i + 4 ) == 0x74 and uint8be ( @a + i + 6 ) == 0x70 ) or for any j in ( 100 .. 200 ) : ( uint8be ( @b + j ) == 0x68 and uint8be ( @b + j + 2 ) == 0x74 and uint8be ( @b + j + 4 ) == 0x74 and uint8be ( @b + j + 6 ) == 0x70 ) or for any k in ( 200 .. 400 ) : ( uint8be ( @c + k ) == 0x68 and uint8be ( @c + k + 2 ) == 0x74 and uint8be ( @c + k + 4 ) == 0x74 and uint8be ( @c + k + 6 ) == 0x70 ) ) and ( ( for any l in ( 14 .. 70 ) : ( uint8be ( @pref_1 + l ) == 0x2f ) ) or ( for any y in ( 16 .. 70 ) : ( uint8be ( @pref_2 + y ) == 0x2f ) ) ) }rule PTESC_exploit_win_ZZ_MalDoc__CVE201711882__Rtf__CA { strings: $equation = "4571756174696F6E" nocase ascii //180000004571756174696F6E $msftedit = "generator Msftedit 6.39.15" nocase ascii //generator Msftedit 6.39.15.1401 $objclass = "objclass weaseoijsd" nocase ascii condition: uint32be ( 0 ) == 0x7B5C7274 and ($equation and ($msftedit or $objclass) or (for any i in (50..350) : (uint8be (@equation + i) == 0x64 and uint8be (@equation + i + 2) == 0x64 and uint8be (@equation + i + 4) == 0x64 and uint8be (@equation + i + 6) == 0x38))) }

IOCs

File indicators

Name	SHA-256	MD5	SHA-1
Методические рекомендации для грузоотправителей-грузополучателей (2022).doc (Guidelines for consignors-consignees (2022).doc)	f2c4281e4d6c11173493b759adfb0eb798ce46650076e7633cf086b6d59fdb98	b3f55d9065dd51a8be2d6c5078866086	9f4a18adaa094eef06ef88e76b6f4ed777f677e7
Будьте_бдительны_Корпоративное_уведомление.doc (Stay_alert_Corporate_Notice.doc)	482aeb3db436e8d531b2746a513fe9a96407cf4458405680a49605e136858ec5	3399deafaa6b91e8c19d767935ae0908	b745032dd5cd6f7eba2187fa3c86c775953a5611
Иранские оценки визита В. Путина в Тегеран.doc (Iranian assessments of V. Putin's visit to Tehran.doc)	2f97374c76ae10c642a57a8b13d25cbdc070c9098c951ea418d1533ac01dc23c	61b6e2040d5815d0135b2850137828d9	df80df54f94d56aa436cdc2713e3bc8160ce43f8
Почему исламский мир не дает Западу изолировать Россию.doc (Why the Islamic world does not allow the West to isolate Russia.doc)	3cf2bda35e88c59bb89e7fdc8fcfd4c46b2b9186e61325d2924e049d775b741f	2b5cec8715e92d87bf6992e003a5651c	9fc804b58ab43fc5f453810a30ea311fc3f5cbe6
leptophis[1].doc	c0e154b10d70b99b5616a2eda6bfe188a49f85ed3aa92d48ec9ce709df9d563f	470c1df23bd825c6e36e1cd5936db912	ba9fc2f0d9f0fcf726a2cbc426f570bea5f22c96
lep[1].hta	a4194555b19ea32680cc23f8f7d42da02b82eba8b64cb5f4630110f4e2c1ddf3	66ecc2285e9d172ceb9f0b0ba030c65c	b5cc0a7ff0d8cd151545cbabcaf23c5486acec95
unbroken.vbs	59066dc428cde7cc55f3c24c2658d3e288f3f072811d86243a85af14bd482744	7ce01fc92fc221cad338cea1cfd43a22	9579b7f3a98657f704575aa4a08ed6ff3d8680a4
unbroken.vbs.vbs	4cb6e224b6b03a2f6ac1ac23e6bf097067018b90493ee94f210f66fbbbbdce77	1aa04f847bd7ec987986ec6e52966b89	8e23ac686bbc958dd85e46a2d4bb6acaee5aa35f
list.ps1	2233c0d4030cc728c2219b1e9c4c05cb262e2ddc7f4ac2f2924767396418c25a	d5a40e2986efd4a182bf564084533763	89364b9d170ab90d25d30649582679c3d7332b91
office.ps1	7fcf7c1dad362283d0a27993df4764e2bbb11857842b80f63d63449b9f2f1fa4	d02ab337bc56214d72b8cabea8bc19b2	81e22a16a6617670c394dbd7ee642eba8e419de7
office.ps1	d9fc6504c8970fefc441c77965937c382b029f1278918d1f54d196859e9f6e7c	077b71298ce31832ae43e834b7e6c080	ee50f3cd04d0fdf5e931ad85bfd464828116279b
rtcpsvc.dll	3e7b066c26ba98d285a41043c739be8767606d9df057ee2f7bcddb7862c00711	f68e64dacd046289d4222098ee421478	ce13a1ae0dd5d537320b77ac8e3d94df6448a82a
lockrail.dll	c5d1de206445f508c1af5f213e46b915b536e4b36ef917c4e826a982dd47c312	acbbc6fea0dbbe7cba511b450cc2b758	94f342f9219cee4f2b91b54809de92d5bb00e93e
holeincorner	8215e918ca3a77424dadac1aebc9a44b8f9840cd1389df0399a9fa4eb6329775	dc3faa6840d1b5fd296d71ee8877254e	53b767ff4fa5c5adc7041389ffd28bb4abda1434
Salzgitters.avi	b8dc70b9ffe06c9ecaf0216ea7948fe718143db10641a23297652693ea026ab3	e5e19040beabb0c0c68fdf4f3978a18b	e68dc027aee851125960ee0559610f43fee581b0
Schultes.wmv	f4e710f515249e8c08ae76284bfb280070e1fd2308e9d9321d92163dfc73be66	45f6f95918efbdcc2c97e3d905635f83	9a1d8a68042b91ee17648606e43907354227d25f

Payload filenames (from the configuration):

callicrates
tinh
amianthium
mandarinduck
cushioning
kingsclover

Email addresses from which malicious emails were sent:

MITRE TTPs

ID	Name	Description
Resource Development
T1583	Acquire Infrastructure	The Cloud Atlas group used servers to store remote templates, as well as cloud storage as a control server
T1585	Establish Accounts	The Cloud Atlas group registered cloud service accounts and tempmail mailboxes
Initial Access
T1566.001	Phishing: Spearphishing Attachment	The Cloud Atlas group sent phishing emails with malicious content
Execution
T1204.002	User Execution: Malicious File	The Cloud Atlas group sent emails with malicious DOC and DOCX files
T1559.001	Inter-Process Communication: Component Object Model	The Cloud Atlas group used COM components in their tools
T1059.001	Command and Scripting Interpreter: PowerShell	The Cloud Atlas group used PowerShell scripts to load and run their components
T1059.005	Command and Scripting Interpreter: Visual Basic	The Cloud Atlas group used Visual Basic scripts to load and run their components
T1203	Exploitation for Client Execution	The Cloud Atlas group used vulnerabilities in Microsoft Office components to launch their malicious components
Persistence
T1547.001	Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder	The Cloud Atlas group used registry keys (autorun) for persistence
Defense Evasion
T1221	Template Injection	The Cloud Atlas group used a remote template injection technique to hide the malicious payload
T1140	Deobfuscate/Decode Files or Information	The Cloud Atlas group encrypts its components to protect them from discovery and analysis
Collection
T1025	Data from Removable Media	The Cloud Atlas group used tools to collect information from various remote devices
T1039	Data from Network Shared Drive	The Cloud Atlas group used tools to collect information from various network devices
T1005	Data from Local System	The Cloud Atlas group used tools to collect information from the file system
T1560.002	Archive Collected Data: Archive via Library	The Cloud Atlas group applies LZNT1 compression to collected data using the WinAPI library
T1560.003	Archive Collected Data: Archive via Custom Method	The Cloud Atlas group used custom data encryption algorithms
T1119	Automated Collection	The Cloud Atlas group used methods of automatic data collection from infected machines
Command and Control (C2)
T1573.001	Encrypted Channel: Symmetric Cryptography	The Cloud Atlas group used AES encryption to hide network communication
T1041	Exfiltration Over C2 Channel	The Cloud Atlas group used a C2 channel to transfer collected data
T1102	Web Service	The Cloud Atlas group used the OpenDrive cloud service as a control server

General TTP countermeasures used by CloudAtlas

Basic protective measures

D3FEND ID	Name of technique D3FEND	Description
D3-SYSVA	System Vulnerability Assessment	Since CloudAtlas exploits vulnerabilities, it is necessary to monitor the vulnerability of systems in the infrastructure and update vulnerable software in a timely manner
D3-SU	Software Update	Since CloudAtlas exploits vulnerabilities, it is necessary to monitor the vulnerability of systems in the infrastructure and update vulnerable software in a timely manner
D3-OTF	Outbound Traffic Filtering	Restrict network traffic to untrusted servers from IOC lists
D3-DNSDL	DNS Denylisting	Block resolution of DNS names from IOC lists

Additional protective measures

D3FEND ID

Name of technique D3FEND

Description

D3-SRA

Sender Reputation Analysis

CloudAtlas group uses free email services, so as an additional measure of protection against phishing, you can specially mark emails from external free services to attract additional attention of the user

D3-UDTA

User Data Transfer Analysis

CloudAtlas grouping downloads data through compromised workstations, so you can use profiling of the amount of data transferred to the Internet by the user to detect anomalies in the case of massive data exfiltration

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