This blog post is based on “IcePeony with the ‘996’ work culture” that we presented at VB2024. We are grateful to Virus Bulletin for giving us the opportunity to present.

https://www.virusbulletin.com/conference/vb2024/abstracts/icepeony-996-work-culture/

tl;dr

We have discovered a previously unknown China-nexus APT group, which we have named “IcePeony”. Due to operational mistakes, they exposed their resources, allowing us to uncover details of their attacks.

• IcePeony is a China-nexus APT group that has been active since at least 2023. They have targeted government agencies, academic institutions, and political organizations in countries such as India, Mauritius, and Vietnam.
• Their attacks typically start with SQL Injection, followed by compromise via webshells and backdoors. Interestingly, they use a custom IIS malware called “IceCache”.
• Through extensive analysis, we strongly believe that IcePeony is a China-nexus APT group, operating under harsh work conditions.

IcePeony

IcePeony is an unknown attack group. Our research shows that they have been active since at least 2023. They mainly target Asian countries, such as India and Vietnam. In the log files we analyzed, there were over 200 attempts to attack various government websites in India.

They use SQL injection attacks on public web servers. If they find a vulnerability, they install a webshell or malware. Ultimately, their goal is to steal credentials.

We believe IcePeony works for China’s national interests. It is possible that they prioritize China’s maritime strategy.

Our research found that IcePeony targeted government and academic institutions in India, political parties in Vietnam, and government institutions in Mauritius. Recently, they may have also attacked Brazil. It is likely that they will expand their targets in the future.

OPSEC fail

In July, we identified a host that was publicly exposing various attack tools, including CobaltStrike and sqlmap, via an open directory. What made this discovery even more compelling was the presence of a zsh_history file.

One of the most interesting findings was the zsh_history file. Similar to bash_history, the zsh_history file records command history. However, zsh_history also logs timestamps, allowing us to pinpoint the exact time each command was executed. This enabled us to construct a highly detailed timeline of the attack.

Unlike a typical timeline created by an IR or SOC analyst, this one offers insight from the attacker’s perspective. We could observe their trial-and-error process and how they executed the intrusion.

The zsh_history was not the only interesting file. There were many others.

For example, IcePeony had configured several helper commands in their alias file, including shortcuts to simplify lengthy commands and commands to quickly access help information.

Here is an example with Mimikatz. By typing “hPass,” the attacker could display basic tutorials for Mimikatz. This improved their effectiveness during attacks.

Intrusion Timeline

We obtained two weeks’ worth of command history from the zsh_history. Let’s go through the events of each day.

On day-1, the attacker attempted SQL injections on several government websites. When the exploit succeeded, they installed a webshell or IceCache, establishing a foothold for the attack. On day-2, they reviewed the domain information of compromised hosts and created accounts for further exploitation. On day three, which was a Sunday, no actions were taken. On day-3, which was a Sunday, they did not perform any actions. It seems the attacker does not work on Sundays. On day-4, they used IceCache to configure proxy rules. We will explain this in more detail later. On day-5, the attacker expanded their reach by attempting more SQL injections on other government websites. On day-6, they used various tools, including IcePeony’s custom tool called StaX and a rootkit called Diamorphine. On day-7, they continued to attack other hosts using tools like URLFinder and sqlmap.

On day-8, they used IceCache to steal information from the compromised environment, especially focusing on domain users. On day-9, they were quiet and only performed connection checks. On day-10, they did nothing since it was a Sunday. On day-11, they used tools like craXcel and WmiExec. They used craXcel, an open-source tool, to unlock password-protected Microsoft Office files. On day-12, they used IceCache to add proxy rules and set persistence with scheduled tasks. On day-13 and day-14, they explored other hosts for further exploitation.

Over the course of two weeks, the attacker utilized a variety of tools and commands to compromise government websites and exfiltrate information.

Tools

IcePeony uses a wide range of tools, with a particular preference for open-source ones. Here, we will highlight only the most distinctive tools they use.

StaX

StaX is a customized variant of the open-source tool Stowaway, a high-performance proxy tool. The attacker enhanced Stowaway with custom processing. Based on development strings, we called this version StaX.

StaX included encryption for communication targets specified in active mode using Custom Base64 and AES.

ProxyChains

ProxyChains is an open-source proxy tool. The attacker used ProxyChains to run script files on victim hosts.

info.sh is a script that collects system information from the compromised environment. It gathers environment information, user information, installed tool versions, network settings, SSH configuration files, and command history.

linux_back.sh is a script for backdoors and persistence. It downloads and runs a backdoor shell script from the server and creates backdoor users.

Interestingly, they installed a rootkit called Diamorphine, which is available on GitHub.

Malware

The IcePeony server contained malware targeting IIS, which we named IceCache. They used IceCache to attack the attack surface server. Additionally, during the investigation, we discovered another related malware, which we called IceEvent. Although no logs of using IceEvent were found. We believe it was used to compromise another computer that was not connected to the internet.

IceCache

IceCache is an ELF64 binary developed in Go language. It is customized based on the open-source software reGeorge.

To facilitate their intrusion operations, they added file transmission commands and command execution functionality.

IceCache module is installed and run on IIS servers. The number of commands change, but they are classified into two types based on authentication tokens. We found files with remaining PDB information. These files were developed by a user named “power” in a project called “cachsess”

The number of commands changes over time, but it includes command execution functions, SOCKS proxy functions, and file transmission functions.

These are the IceCache modules found so far. The first sample we are aware of was compiled in August 2023 and submitted to VirusTotal in October. Since there is no discrepancy between the compille time and the first submission, we believe the dates are reliable.

Many new samples have also been found since 2024. Most of the submitters are from India, which matches the victim information we have gathered from OpenDir data.

The number of commands has change over time. It is show that the malware’s developers have made improvements while continuing their intrusion operations.

IceEvent

IceEvent is a simple passive-mode backdoor that installed as a service.

Two types have been identified based on the command format. Both types only have the minimum necessary commands. The older type was discovered in September 2023, and several new types were found in April of this year. All of these were submitted from India.

Similarities

We believe that IceEvent was developed because a simple passive backdoor was needed during intrusions, based on code similarities with IceCache. Both IceCache and IceEvent use the same key for XOR to encode communication data. And PDB information shows that the same developer created both malware.

This is the XOR-based data encoding process used for communication data, which is equal to both malware.

This is the command execution process equal to both malware. Since the function calls and branching processes are exactly the same, we believe they were compiled from the same source code. Other commands also match perfectly.

The communication data of IceCache and IceEvent is only encoded using the XOR process mentioned earlier, making it easy to decode. Here is an example of decoding the data during command execution.

Attribution

We investigated the attacker’s activity times based on the timestamp information in the zsh_history file. As a result, we found that the attacker is likely operating in the UTC+8 time zone. Surprisingly, the attacker works from 8 a.m. to 10 p.m., which is a 14-hour workday. They are remarkably diligent workers.

Similarly, we investigated the changes in activity based on the day of the week. It seems that the attackers work six days a week. While they are less active on Fridays and Saturdays, their only full day off appears to be Sunday. This investigation suggests that the attackers are not conducting these attacks as personal activities, but are instead engaging in them as part of organized, professional operations.

By the way, have you heard of the term “996 working hour system”? This term originated in China’s IT industry. In China’s IT industry, long working hours see as a problem. It refers to working from 9 a.m. to 9 p.m.,six days a week. Such hard work conditions are called the “996 working hour system”. IcePeony might be working under the 996 working hour system.

https://en.wikipedia.org/wiki/996_working_hour_system

Next, There is a very simple example to consider when discussing attribution. IcePeony sometimes includes Simplified Chinese comments in the tools they use. Here, we provide an example of a wrapper script for the IceCache Client. From this, we can conclude that IcePeony is a threat actor from a region where Simplified Chinese is commonly used.

IcePeony uses an original malware called IceCache. As previously mentioned, IceCache is based on reGeorge. More specifically, IceCache contains a string referring to a project named reGeorgGo.

Upon investigating reGeorgGo, We found that it was developed by a Chinese security engineer. There is no other information about this project on the internet, aside from the developer’s blog. It was a not well-known tool. However, the publicly available reGeorgGo is a tool with only three arguments, where as IceCache has more commands added to it.

https://github.com/zz1gg/secdemo/tree/main/proxy/reGeorgGo

Let’s examine attribution from another side. In this attack campaign, IcePeony targeted India, Mauritius, and Vietnam. While attacks on India and Vietnam are generally not uncommon. What about Mauritius?

Mauritius is a small country located in the Indian Ocean. Interestingly, Mauritius has recently formed a cooperation with India. They are wary of China’s expansion into the Indian Ocean and have begun various forms of collaboration to counter this influence.

https://www.mea.gov.in/newsdetail1.htm?12042/

We summarize the attribution information using the Diamond Model.

IcePeony consists of Simplified Chinese speakers who show interest in the governments of Indian Ocean countries and work under the 996 working hour system.

They prefer open-source software developed in Chinese-speaking regions and use their original malware, IceCache and IceEvent. In attacks on the Indian government, they used VPSs located in the Indian region. Additionally, the governments and education sectors in Mauritius and Vietnam were also targeted.

Wrap-Up

In this blog post, we introduced IcePeony. IcePeony is a newly emerging attack group. Our investigation shows that they have been active since at least 2023. Their primary targets are countries in Asia, such as India and Vietnam.

The log files we analyzed recorded attempts to attack over 200 different Indian government websites. IcePeony typically attempts SQL Injection attacks on publicly accessible web servers. If vulnerabilities are found, they install web shells or execute malware. Ultimately, they aim to steal credentials.

We suspect that IcePeony operates as a group of individuals conducting cyberattacks in support of China’s national interests, possibly in connection with China’s maritime strategy. They remain active, and we must continue monitoring their activities closely moving forward.

IoCs

IP

• 165[.]22.211.62
• 64[.]227.133.248
• 173[.]208.156.19
• 173[.]208.156.144
• 154[.]213.17.225
• 103[.]150.186.219
• 63[.]141.255.16
• 204[.]12.205.10
• 107[.]148.37.63
• 103[.]99.60.119
• 154[.]213.17.237
• 45[.]195.205.88
• 154[.]213.17.244
• 103[.]99.60.93
• 149[.]115.231.17
• 149[.]115.231.39
• 103[.]99.60.108

Domain

• d45qomwkl[.]online
• k9ccin[.]com
• k8ccyn[.]com
• 88k8cc[.]com
• googlesvn[.]com

IceCache

• 484e274077ab6f9354bf71164a8edee4dc4672fcfbf05355958785824fe0468f
• 5b16d1533754c9e625340c4fc2c1f76b11f37eb801166ccfb96d2aa02875a811
• ceb47274f4b6293df8904c917f423c2f07f1f31416b79f3b42b6d64e65dcfe1b
• e5f520d95cbad6ac38eb6badbe0ad225f133e0e410af4e6df5a36b06813e451b
• d1955169cd8195ecedfb85a3234e4e6b191f596e493904ebca5f44e176f3f950
• 11e90e2458a97957064a3d3f508fa6dadae19f632b45ff9523b7def50ebacb63
• de8f58f008ddaa60b5cf1b729ca03f276d2267e0a80b584f2f0723e0fac9f76c
• b8d030ed55bfb6bc4fdc9fe34349ef502561519a79166344194052f165d69681
• 535586af127e85c5561199a9a1a3254d554a6cb97200ee139c5ce23e68a932bd
• 0b8b10a2ff68cb2aa3451eedac4a8af4bd147ef9ddc6eb84fc5b01a65fca68fd
• 5fd5e99fc503831b71f4072a335f662d1188d7bc8ca2340706344fb974c7fe46
• 3eb56218a80582a79f8f4959b8360ada1b5e471d723812423e9d68354b6e008c
• a66627cc13f827064b7fcea643ab31b34a7cea444d85acc4e146d9f2b2851cf6
• 0eb60e4c5dc7b06b719e9dbd880eb5b7514272dc0d11e4760354f8bb44841f77

IceEvent

• 80e831180237b819e14c36e4af70304bc66744d26726310e3c0dd95f1740ee58
• 9a0b0439e6fd2403f764acf0527f2365a4b9a98e9643cd5d03ccccf3825a732e
• 9aba997bbf2f38f68ad8cc3474ef68eedd0b99e8f7ce39045f1d770e2af24fea
• bc94da1a066cbb9bdee7a03145609d0f9202b426a52aca19cc8d145b4175603b

Introduction

A few days ago, we came across a peculiar file. It looked like some kind of builder, and a quick glance at the settings piqued our interest. It appeared to be a ShadowPad builder, probably created around 2021.

ShadowPad builders became a topic of conversation around the time of the i-Soon leak, but we had never seen the actual builder ourselves. This is likely true for most of you as well.

We were so intrigued that we carefully investigated this builder and reviewed past attack campaigns. In this article, we will share how attackers build ShadowPad, what we discovered through our investigation, and our insights.

Our investigation is still ongoing. We would love to engage in active discussions with you. If you have any opinions or comments, please feel free to contact us.

[Note] What we discovered this time is a builder. It does not include a controller. Therefore, it is not possible to control what is generated by this builder. In other words, this builder alone is not meaningful in the real world.

Background

In June 2024, we happened to read a research memo from a year ago. We often read past memos for a change of pace. In doing so, we recalled an attack on Kyrgyzstan in April 2023.

https://x.com/nao_sec/status/1648960199938707456

This attack involved a file resembling a RoyalRoad RTF, which prompted our investigation at the time. Opening this RTF file with a vulnerable version of Microsoft Word displayed a decoy file related to Kyrgyzstan’s cybersecurity, while simultaneously writing and executing several files to the disk. As a result, a CobaltStrike beacon was executed.

The loader that decrypted and executed the beacon resembled Casper Loader. Casper Loader is familiar to threat researchers specializing in East Asia and has been reported to be used in attacks by Tick¹². Our friend @aRtAGGI conducted similar analyses at the time.

https://x.com/aRtAGGI/status/1649184131090087938

We later found that a similar attack had been carried out against Kazakhstan after searching our past database. The attack on Kazakhstan was older than the one on Kyrgyzstan, occurring around November 2022. In this case, the same loader executed from the RTF file eventually ran the CobaltStrike beacon.

Information about the RTF files used in the attacks on Kyrgyzstan and Kazakhstan is listed in the IoC sheet from our previous research on RoyalRoad RTF³⁴. We have identified these as U-4. If you are interested, please refer to the IoC sheet.

https://nao-sec.org/jsac2020_ioc.html

Let’s return to the present. To investigate recent attack samples, we executed a search query based on the characteristics of the loader used in the attack on Kyrgyzstan.

exports:IEE2 exports:LoadLibraryShim2 exports:LoadStringRC2

We found an unusual file posted in May 2024. This data was embedded in the resource section of another file. We downloaded and executed the original file. To our surprise, it was a ShadowPad builder.

CasperVMakerHTTPx86

When launching the ShadowPad builder, which calls itself CasperVMakerHTTPx86, the following screen appears. There are several tabs, each with various settings.

• First
• Install
• Inject
• Online
• Proxy
• DNS

These items are very similar to the reported architecture of ShadowPad⁵. This suggests that these tabs are configuration items for each module. The settings for each item are as follows:

Let’s try building ShadowPad. By clicking the “Build EXE x86” button, ShadowPad is generated. If the build is successful, an EXE file and a DLL file are created.

The EXE file is a legitimate AppLaunch. It loads the mscoree.dll in the same directory via DLL Side-Loading. The DLL file is the Casper Loader, which decodes and executes the ShadowPad shellcode stored internally.

Comparison with Similar Samples

ShadowPad loaders exhibit several patterns, but those generated using this builder are decoded using a custom XOR with constants.

There are many samples with similar characteristics, but we will introduce two of them.

Sample-1

According to Macnica’s report², Tick uses Casper Loader to execute ShadowPad. Comparing this Casper Loader with the loader created using the builder reveals that while the Macnica sample contains junk code and different fixed values, the algorithm is the same.

Sample-2

A report released by the FBI in December 2021⁶ reported an attack exploiting CVE-2021-44515 where ShadowPad was used. The AppLaunch.exe and mscoree.dll in this case used Casper Loader to execute ShadowPad.

Comparing this Casper Loader with the one created using the builder shows that the algorithm and fixed values are identical. Although API Hashing is not used, it is a highly similar sample.

ShadowPad Community

As you know, ShadowPad is commercial software sold for profit. According to SentinelOne’s report from 2021⁵, ShadowPad is sold to various targeted attack groups, and there is speculation that whg and Rose are involved in its development. The i-Soon leak in February 2024 reported that i-Soon was selling software that appeared to be ShadowPad (including source code and training)⁷.

As various researchers have reported^{256891011121314151617181920212223242526272829303132333435363738}, many targeted attack groups use ShadowPad. These can be broadly categorized into two groups: attack groups associated with the MSS, like APT41, and those associated with the PLA, like Tick.

As previously mentioned, it is generally believed that whg and Rose were involved in ShadowPad’s development. There is no compelling reason to refute this, so we will proceed with this assumption. According to a U.S. government report related to APT41³⁹, Rose (Tan Dailin) was involved in APT41. Seven individuals were indicted for their involvement with APT41, with Rose (and Zhang Haoran) being particularly noted for their involvement in both BARIUM and LEAD, making them key figures in APT41’s activities. This background suggests that BARIUM was the earliest adopter of ShadowPad, followed by LEAD.

In contrast, the PLA has many more attack groups using ShadowPad than the MSS. This is generally because many researchers have given them different names, and their relationships are not sufficiently organized. If you are a researcher, you probably have more organized information in your mind (or within your organization). Of course, we understand and accept this. However, to keep things simple, we will exclude such discussions in this article and share how we organized this information within nao_sec. Interestingly, all these attack groups used the RoyalRoad RTF Weaponizer. Is this just a coincidence? ShadowPad and RoyalRoad RTF Weaponizer may be shared through the same channels.

Conclusion

In this article, we introduced the ShadowPad builder. ShadowPad, widely used by various targeted attack groups as a successor to PlugX, had limited information available about its builder until now. This article sheds light on how attackers build ShadowPad.

We also organized the relationships between attack groups using ShadowPad. Our research is still ongoing. We would love to engage in active discussions. If you have any opinions or comments, please contact us. We look forward to hearing from you.

Acknowledgments

We received a lot of help from our friends in writing this article. While we won’t name individuals here, we are immensely grateful to the many supportive reviewers. We want to take this opportunity to express our deepest gratitude to you.

References