Researchers at Trend Micro have discovered some new Linux-based ransomware that’s being used to attack VMware ESXi servers, a bare-metal hypervisor for creating and running several virtual machines (VMs) that share the same hard drive storage. Called Cheerscrypt, the bad app is following in the footsteps of other ransomware programs—such as LockBit, Hive and RansomEXX—that have found ESXi an efficient way to infect many computers at once with malicious payloads.

Roger Grimes, a defense evangelist with security awareness training provider KnowBe4, explains that most of the world’s organizations operate using VMware virtual machines. “It makes the job of ransomware attackers far easier because they can encrypt one server—the VMware server—and then encrypt every guest VM it contains. One compromise and encryption command can easily encrypt dozens to hundreds of other virtually run computers all at once.”

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Executive summary

AT&T Alien Labs™ has been tracking a new IoT botnet dubbed “EnemyBot”, which is believed to be distributed by threat actor Keksec. During our investigations, Alien Labs has discovered that EnemyBot is expanding its capabilities, exploiting recently identified vulnerabilities (2022), and now targeting IoT devices, web servers, Android devices and content management system (CMS) servers. In addition, the malware base source code can now be found online on Github, making it widely accessible.

Key takeaways:

EnemyBot’s base source code can be found on Github, making it available to anyone who wants to leverage the malware in their attacks.
The malware is rapidly adopting one-day vulnerabilities as part of its exploitation capabilities.
Services such as VMware Workspace ONE, Adobe ColdFusion, WordPress, PHP Scriptcase and more are being targeted as well as IoT and Android devices.
The threat group behind EnemyBot, Keksec, is well-resourced and has the ability to update and add new capabilities to its arsenal of malware on a daily basis (see below for more detail on Keksec)

Background

First discovered by Securonix in March 2022 and later detailed in an in-depth analysis by Fortinet, EnemyBot is a new malware distributed by the threat actor “Keksec” targeting Linux machines and IoT devices.

According to the malware Github’s repository, EnemyBot derives its source code from multiple botnets to a powerful and more adjustable malware. The original botnet code that EnemyBot is using includes: Mirai, Qbot, and Zbot. In addition, the malware includes custom development (see figure 1).

Figure 1. EnemyBot page on Github.

The Keksec threat group is reported to have formed back in 2016 by a number of experienced botnet actors. In November 2021, researchers from Qihoo 360 described in detail the threat actor’s activity in a presentation, attributing to the Keksec the development of botnets for different platforms including Windows and Linux:

Linux based botnets: Tsunami and Gafgyt
Windows based botnets: DarkIRC, DarkHTTP
Dual systems: Necro (developed in Python)

Source code analysis

The developer of the Github page on EnemyBot self describes as a “full time malware dev,” that is also available for contract work. The individual states their workplace as “Kek security,” implying a potential relationship with the broader Keksec group (see figure 2).

Figure 2. EnemyBot developer description.

The malware repository on Github contains four main sections:

cc7.py

This module is a Python script file that downloads all dependencies and compiles the malware into different OS architectures including x86, ARM, macOS, OpenBSD, PowerPC, MIPS, and more (see figure 3)

Figure 3. Compiling malware source code to macOS executable.

Once compilation is complete, the script then creates a batch file ‘update.sh’ which is used by the bot as a downloader that is then delivered to any identified vulnerable targets to spread the malware.

Figure 4. Generated `update.sh` file to spread EnemyBot on different architectures.

enemy.c

This is the main bot source code. Though it is missing the main exploitation function, it includes all other functionality of the malware and the attacks the bot supports by mixing the various botnet source codes as mentioned above (Mirai, Qbot, and Zbot) — mainly Mirai and Qbot (see figure 5).

 

Figure 5. EnemyBot source code.

hide.c

This module is compiled and manually executed to encode / decode the malware’s strings by the attacker to hide strings in binary. For that, the malware is using a simple swap table, in which each char is replaced with a corresponding char in the table (see in figure 6).

Figure 6. String decode.

servertor.c

Figure 7 shows the command-and-control component (C&C) botnet controller. C&C will be executed on a dedicated machine that is controlled by the attacker. It can control and send commands to infected machines. (figure 7)

Figure 7. C&C component.

New variant analysis

Most of EnemyBot functionality relates to the malware’s spreading capabilities, as well as its ability to scan public-facing assets and look for vulnerable devices. However, the malware also has DDoS capabilities and can receive commands to download and execute new code (modules) from its operators that give the malware more functionality.

In new variants of EnemyBot, the malware added a webscan function containing a total of 24 exploits to attack vulnerabilities of different devices and web servers (see figure 8).

Figure 8. EnemyBot calls for a new function “webscan_xywz”.

To perform these functions, the malware randomly scans IP addresses and when it gets a response via SYN/ACK, EnemyBot then scans for vulnerabilities on the remote server by executing multiple exploits.

The first exploit is for the Log4j vulnerability discovered last year as CVE-2021-44228 and CVE-2021-45046:

Figure 9. Exploiting the Log4J vulnerability.

The malware also can adopt new vulnerabilities within days of those vulnerabilities being discovered. Some examples are Razer Sila (April 2022) which was published without a CVE (see figure 10) and a remote code execution (RCE) vulnerability impacting VMWare Workspace ONE with CVE-2022-22954 the same month (see figure 11).

Figure 10. Exploiting vulnerability in Razar Sila.

Figure 11. Exploiting vulnerability in VMWare Workspace ONE.

EnemyBot has also begun targeting content management systems (e.g. WordPress) by searching for vulnerabilities in various plugins, such as “Video Synchro PDF” (see figure 12).

Figure 12. EnemyBot targeting WordPress servers.

In the example shown in figure 12, notice that the malware elevates a local file inclusion (LFI) vulnerability into a RCE by injecting malicious code into the ‘/proc/self/environ’. This method is not new and was described in 2009. The malware uses LFI to call ‘environ’ and passes the shell command in the user agent http header.

Another example of how the malware uses this method is shown in figure 13. In this example the malware is exploiting a vulnerability in DBltek GoIP.

Figure 13. Executing shell command through LFI vulnerability in DBltek.

After infection, EnemyBot will wait for further commands from its C&C. However, in parallel it will also further propogate by scanning for additional vulnerable devices. Alien Labs has listed below the commands the bot can receive from its C&C (accurate as of the publishing of this article). 

In case an Android device is connected through USB, or Android emulator running on the machine, EnemyBot will try to infect it by executing shell command. (figure 14)

Figure 14. EnemyBot “adb_infect” function to attack Android devices.

Command

Action

SH

Execute shell command

PING

Ping to server, wait for command

LDSERVER

Change loader server for payload.

TCPON

Turn on sniffer.

RSHELL

Create a reverse shell on an infected machine.

TCPOFF

Turn off sniffer.

UDP

Start UDP flood attack.

TCP

Start TCP flood attack.

HTTP

Start HTTP flood attack.

HOLD

Start TCP connection flooder.

TLS

Start TLS attack, start handshake without closing the socket.

STD

Start non spoofed UDP flooder.

DNS

Start DNS flooder.

SCANNER ON | OFF

Start/Stop scanner – scan and infect vulnerable devices.

OVH

Start DDos attack on OVH.

BLACKNURSE

Start ICMP flooder.

STOP

Stop ongoing attacks. kill child processes

ARK

Start targeted attack on ARK: Survivor Evolved video game server.

ADNS

Receive targets list from C&C and start DNS attack.

ASSDP

Start SSDP flood attack.

We have also listed the current vulnerabilities EnemyBot uses. As mentioned, some of them have not been assigned a CVE yet. (As of the publishing of this article.)

CVE Number

Affected devices

CVE-2021-44228, CVE-2021-45046

Log4J RCE

CVE-2022-1388

F5 BIG IP RCE

No CVE (vulnerability published on 2022-02)

Adobe ColdFusion 11 RCE

CVE-2020-7961

Liferay Portal – Java Unmarshalling via JSONWS RCE

No CVE (vulnerability published on 2022-04)

PHP Scriptcase 9.7 RCE

CVE-2021-4039

Zyxel NWA-1100-NH Command injection

No CVE (vulnerability published on 2022-04)

Razar Sila – Command injection

CVE-2022-22947

Spring Cloud Gateway – Code injection vulnerability

CVE-2022-22954

VMWare Workspace One RCE

CVE-2021-36356, CVE-2021-35064

Kramer VIAware RCE

No CVE (vulnerability published on 2022-03)

WordPress Video Synchro PDF plugin LFI

No CVE (vulnerability published on 2022-02)

Dbltek GoIP LFI

No CVE(vulnerability published on 2022-03)

WordPress Cab Fare Calculator plugin LFI

No CVE(vulnerability published on 2022-03)

Archeevo 5.0 LFI

CVE-2018-16763

Fuel CMS 1.4.1 RCE

CVE-2020-5902

F5 BigIP RCE

No CVE (vulnerability published on 2019)

ThinkPHP 5.X RCE

No CVE (vulnerability published on 2017)

Netgear DGN1000 1.1.00.48 ‘Setup.cgi’ RCE

CVE-2022-25075

TOTOLink A3000RU command injection vulnerability

CVE-2015-2051

D-Link devices – HNAP SOAPAction – Header command injection vulnerability

CVE-2014-9118

ZHOME < S3.0.501 RCE

CVE-2017-18368

Zyxel P660HN – unauthenticated command injection

CVE-2020-17456

Seowon SLR 120 router RCE

CVE-2018-10823

D-Link DWR command injection in various models

Recommended actions

Maintain minimal exposure to the Internet on Linux servers and IoT devices and use a properly configured firewall.
Enable automatic updates to ensure your software has the latest security updates.
Monitor network traffic, outbound port scans, and unreasonable bandwidth usage.

Conclusion

Keksec’s EnemyBot appears to be just starting to spread, however due to the authors’ rapid updates, this botnet has the potential to become a major threat for IoT devices and web servers. The malware can quickly adopt one-day vulnerabilities (within days of a published proof of concept). This indicates that the Keksec group is well resourced and that the group has developed the malware to take advantage of vulnerabilities before they are patched, thus increasing the speed and scale at which it can spread.

Detection methods

The following associated detection methods are in use by Alien Labs. They can be used by readers to tune or deploy detections in their own environments or for aiding additional research.

SURICATA IDS SIGNATURES

Log4j sids: 2018202, 2018203, 2034647, 2034648, 2034649, 2034650, 2034651, 2034652, 2034653, 2034654, 2034655, 2034656, 2034657, 2034658, 2034659, 2034660, 2034661, 2034662, 2034663, 2034664, 2034665, 2034666, 2034667, 2034668, 2034671, 2034672, 2034673, 2034674, 2034676, 2034699, 2034700, 2034701, 2034702, 2034703, 2034706, 2034707, 2034708, 2034709, 2034710, 2034711, 2034712, 2034713, 2034714, 2034715, 2034716, 2034717, 2034723, 2034743, 2034744, 2034747, 2034748, 2034749, 2034750, 2034751, 2034755, 2034757, 2034758, 2034759, 2034760, 2034761, 2034762, 2034763, 2034764, 2034765, 2034766, 2034767, 2034768, 2034781, 2034782, 2034783, 2034784, 2034785, 2034786, 2034787, 2034788, 2034789, 2034790, 2034791, 2034792, 2034793, 2034794, 2034795, 2034796, 2034797, 2034798, 2034799, 2034800, 2034801, 2034802, 2034803, 2034804, 2034805, 2034806, 2034807, 2034808, 2034809, 2034810, 2034811, 2034819, 2034820, 2034831, 2034834, 2034835, 2034836, 2034839, 2034886, 2034887, 2034888, 2034889, 2034890, 2838340, 2847596, 4002714, 4002715

4001913: AV EXPLOIT LifeRay RCE (CVE-2020-7961)

4001943: AV EXPLOIT Liferay Portal Java Unmarshalling RCE (CVE-2020-7961)

4002589: AV EXPLOIT LifeRay Remote Code Execution – update-column (CVE-2020-7961)

2031318: ET CURRENT_EVENTS 401TRG Liferay RCE (CVE-2020-7961)

2031592: ET WEB_SPECIFIC_APPS Liferay Unauthenticated RCE via JSONWS Inbound (CVE-2020-7961)

2035955: ET EXPLOIT Razer Sila Router – Command Injection Attempt Inbound (No CVE)

2035956: ET EXPLOIT Razer Sila Router – LFI Attempt Inbound (No CVE)

2035380: ET EXPLOIT VMware Spring Cloud Gateway Code Injection (CVE-2022-2294) (set)

2035381: ET EXPLOIT VMware Spring Cloud Gateway Code Injection (CVE-2022-2294)

2035876: ET EXPLOIT VMWare Server-side Template Injection RCE (CVE-2022-22954)

2035875: ET EXPLOIT VMWare Server-side Template Injection RCE (CVE-2022-22954)

2035874: ET EXPLOIT VMWare Server-side Template Injection RCE (CVE-2022-22954)

2036416: ET EXPLOIT Possible VMware Workspace ONE Access RCE via Server-Side Template Injection Inbound (CVE-2022-22954)

4002364: AV EXPLOIT Fuel CMS RCE (CVE-2018-16763)

2030469: ET EXPLOIT F5 TMUI RCE vulnerability CVE-2020-5902 Attempt M1

2030483: ET EXPLOIT F5 TMUI RCE vulnerability CVE-2020-5902 Attempt M2

2836503: ETPRO EXPLOIT Attempted THINKPHP < 5.2.x RCE Inbound

2836504: ETPRO EXPLOIT Attempted THINKPHP < 5.2.x RCE Outbound

2836633: ETPRO EXPLOIT BlackSquid Failed ThinkPHP Payload Inbound

2026731: ET WEB_SERVER ThinkPHP RCE Exploitation Attempt

2024916: ET EXPLOIT Netgear DGN Remote Command Execution

2029215: ET EXPLOIT Netgear DGN1000/DGN2200 Unauthenticated Command Execution Outbound

2034576: ET EXPLOIT Netgear DGN Remote Code Execution

2035746: ET EXPLOIT Totolink – Command Injection Attempt Inbound (CVE-2022-25075)

4001488: AV TROJAN Mirai Outbound Exploit Scan, D-Link HNAP RCE (CVE-2015-2051)

2034491: ET EXPLOIT D-Link HNAP SOAPAction Command Injection (CVE-2015-2051)

4000095: AV EXPLOIT Unauthenticated Command Injection (ZyXEL P660HN-T v1)

4002327: AV TROJAN Mirai faulty Zyxel exploit attempt

2027092: ET EXPLOIT Possible ZyXEL P660HN-T v1 RCE

4002226: AV EXPLOIT Seowon Router RCE (CVE-2020-17456)

2035950: ET EXPLOIT SEOWON INTECH SLC-130/SLR-120S RCE Inbound M1 (CVE-2020-17456)

2035951: ET EXPLOIT SEOWON INTECH SLC-130/SLR-120S RCE Inbound M2 (CVE-2020-17456)

2035953: ET EXPLOIT D-Link DWR Command Injection Inbound (CVE-2018-10823)

 

AGENT SIGNATURES

Java Process Spawning Scripting Process

 

Java Process Spawning WMIC

Java Process Spawning Scripting Process via Commandline (For Jenkins servers)

Suspicious process executed by Jenkins Groovy scripts (For Jenkins servers)

Suspicious command executed by a Java listening process (For Linux servers)

Associated indicators (IOCs)

The following technical indicators are associated with the reported intelligence. A list of indicators is also available in the OTX Pulse. Please note, the pulse may include other activities related but out of the scope of the report.

TYPE

INDICATOR

DESCRIPTION

IP ADDRESS

80.94.92[.]38

Malware C&C

SHA256

7c0fe3841af72d55b55bc248167665da5a9036c972acb9a9ac0a7a21db016cc6

Malware hash

SHA256

2abf6060c8a61d7379adfb8218b56003765c1a1e701b346556ca5d53068892a5

Malware hash

SHA256

7785efeeb495ab10414e1f7e4850d248eddce6be91738d515e8b90d344ed820d

Malware hash

SHA256

8e711f38a80a396bd4dacef1dc9ff6c8e32b9b6d37075cea2bbef6973deb9e68

Malware hash

SHA256

31a9c513a5292912720a4bcc6bd4918fc7afcd4a0b60ef9822f5c7bd861c19b8

Malware hash

SHA256

139e1b14d3062881849eb2dcfe10b96ee3acdbd1387de82e73da7d3d921ed806

Malware hash

SHA256

4bd6e530db1c7ed7610398efa249f9c236d7863b40606d779519ac4ccb89767f

Malware hash

SHA256

7a2a5da50e87bb413375ecf12b0be71aea4e21120c0c2447d678ef73c88b3ba0

Malware hash

SHA256

ab203b50226f252c6b3ce2dd57b16c3a22033cd62a42076d09c9b104f67a3bc9

Malware hash

SHA256

70674c30ed3cf8fc1f8a2b9ecc2e15022f55ab9634d70ea3ba5e2e96cc1e00a0

Malware hash

SHA256

f4f9252eac23bbadcbd3cf1d1cada375cb839020ccb0a4e1c49c86a07ce40e1e

Malware hash

SHA256

6a7242683122a3d4507bb0f0b6e7abf8acef4b5ab8ecf11c4b0ebdbded83e7aa

Malware hash

SHA256

b63e841ded736bca23097e91f1f04d44a3f3fdd98878e9ef2a015a09950775c8

Malware hash

SHA256

4869c3d443bae76b20758f297eb3110e316396e17d95511483b99df5e7689fa0

Malware hash

SHA256

cdf2c0c68b5f8f20af448142fd89f5980c9570033fe2e9793a15fdfdadac1281

Malware hash

 

Mapped to MITRE ATT&CK

The findings of this report are mapped to the following MITRE ATT&CK Matrix techniques:

TA0001: Initial Access:

T1190: Exploit Public-Facing Application

TA0008: Lateral Movement:

T1210: Exploitation of Remote Services
T1021: Remote Services

TA0011: Command and Control

T1132: Data Encoding
T1001: Data Obfuscation
T1030: Proxy:

003: Multi-hop Proxy

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