Cybaze -Yoroi ZLAB revealed interesting a hidden connection between the AZORult toolkit and specific Gootkit payload.

Introduction

In the last days, a huge attack campaign hit several organizations across the Italian cyberspace, as stated on bulletin N020219 the attack waves tried to impersonate legit communication from a known Express Courier. However, a deeper analysis by Cybaze -Yoroi ZLAB revealed interesting hidden aspects, spotting a connection between the AZORult toolkit and a particular Gootkitpayload.

Technical analysis

Stage 1 – The Attached Javascript

Most of the infection attempts started with a particular email attachment: a compressed archive containing stealthy JavaScript code, most of the times able to avoid antivirus detection during the initial stages of the attack campaigns.



Hash 12791e14ba82d36d434e7c7c0b81c7975ce802a430724f134b7e0cce5a7bb185 Threat malicious js Desc Obfuscated malicious JS. This download first component and keep communication with C2 server.

Table 1: Generic information about malicious js file

This JS file is an obfuscated dropper with the purpose to download another component from a “safe” remote location:

Figure 1: Snippet from the JavaScript attachment

It contacts two distinct servers, googodsgld.]com and driverconnectsearch.]info. The behaviour of this sort of JavaScript stager is as essential as interesting: it downloads other executable code able to virtually do anything the attacker wants. This kind of pattern and the simplicity of the code itself remotely resemble the Brushaloader threat, a known dropper/stager written in VBScript and contacting its remote infrastructures in a similar manner. We can hypothesize that the malware writers may have emulated the Brushaloader stager functionalities, creating a sort of custom version exploiting the same mechanism.

Figure 2: Classic Brushaloader sample (left) along with the recent Javascript stager (right)

Figure 3: Encrypted communication with driverconnectsearch[.]info server

After the first contact attempt to googodsgld[.]com, the script communicates with the other destination and retrieves a Cabinet Archive encoded within the chunk of executable javascript code returned by driverconnectsearch[.]info. Then it stores it in “%APPDATA%\Local\Temp\”.



As shown in Figure 3, the first characters of the encoded payload string are “TVNDRg” which translates to “MSCF”: standard header of the Microsoft Cabinet compressed file format.

Figure 4: Javascript downloaded from diverconnectsearch[.]info server.

Stage 2 – The Cabinet

Actually, this .CAB archive is just a shell for a PE32 executable file:



Hash 2274174ed24425f41362aa207168b491e6fb55cab208116070f91c049946097a Threat RuntimeBroker5.exe Desc First component downloaded by malicious js file.

Table 2: Generic information about RuntimeBroker5.exe (AZORult)

Executing the RuntimeBroker5.exe sample, seems it behaves as another dropper: it downloads two other components from the remote server “hairpd[.]com”.



Figure 5: RuntimeBroker5.exe process execution

The sample file actually does not perform only this downlaod. Here one of the key point of the article: it also establishes a communication channel with the AZORult C2 host “ssl.]admin.]itybuy.]it”.



The network packet exchanged with the server confirms this identification due to the known communication patterns and the dynamic analysis also shows info-stealing behaviours compatible with the identified threat.



As shown in the following figure, the written files in “%APPDATA%\Local\Temp\” path closely match AZORult analysis described by Unit42 research group.

Figure 6: Evidence of the similarity of RuntimeBroker5.exe and AZORult malware variant analyzed by UNIT42

Figure 7: C2 Communication comparison

During the dynamic analysis, the RuntimeBroker5.exe sample received a sort of configuration file from the C2 server. We extracted it from the running malware image and decoded it:

firefox.exe SOFTWARE\Wow6432Node\Mozilla\Mozilla Firefox\ SOFTWARE\Mozilla\Mozilla Firefox SOFTWARE\Clients\StartMenuInternet\FIREFOX.EXE\shell\open\command SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\firefox.exe %appdata%\Mozilla\Firefox\Profiles\ MozillaFireFox CurrentVersion Install_Directory nss3.dll thunderbird.exe SOFTWARE\Wow6432Node\Mozilla\Mozilla Thunderbird\ SOFTWARE\Mozilla\Mozilla Thunderbird SOFTWARE\Classes\ThunderbirdEML\DefaultIcon %appdata%\Thunderbird\Profiles\ ThunderBird SELECT host, path, isSecure, expiry, name, value FROM moz_cookies SELECT fieldname, value FROM moz_formhistory NSS_Init PK11_GetInternalKeySlot PK11_Authenticate PK11SDR_Decrypt NSS_Shutdown PK11_FreeSlot logins.json logins hostname timesUsed encryptedUsername encryptedPassword cookies.sqlite formhistory.sqlite %LOCALAPPDATA%\Google\Chrome\User Data\ %LOCALAPPDATA%\Google\Chrome SxS\User Data\ %LOCALAPPDATA%\Xpom\User Data\ %LOCALAPPDATA%\Yandex\YandexBrowser\User Data\ %LOCALAPPDATA%\Comodo\Dragon\User Data\ %LOCALAPPDATA%\Amigo\User Data\ %LOCALAPPDATA%\Orbitum\User Data\ %LOCALAPPDATA%\Bromium\User Data\ %LOCALAPPDATA%\Chromium\User Data\ %LOCALAPPDATA%\Nichrome\User Data\ %LOCALAPPDATA%\RockMelt\User Data\ %LOCALAPPDATA%\360Browser\Browser\User Data\ %LOCALAPPDATA%\Vivaldi\User Data\ %APPDATA%\Opera Software\ %LOCALAPPDATA%\Go!\User Data\ %LOCALAPPDATA%\Sputnik\Sputnik\User Data\ %LOCALAPPDATA%\Kometa\User Data\ %LOCALAPPDATA%\uCozMedia\Uran\User Data\ %LOCALAPPDATA%\QIP Surf\User Data\ %LOCALAPPDATA%\Epic Privacy Browser\User Data\ %APPDATA%\brave\ %LOCALAPPDATA%\CocCoc\Browser\User Data\ %LOCALAPPDATA%\CentBrowser\User Data\ %LOCALAPPDATA%\7Star\7Star\User Data\ %LOCALAPPDATA%\Elements Browser\User Data\ %LOCALAPPDATA%\TorBro\Profile\ %LOCALAPPDATA%\Suhba\User Data\ %LOCALAPPDATA%\Safer Technologies\Secure Browser\User Data\ %LOCALAPPDATA%\Rafotech\Mustang\User Data\ %LOCALAPPDATA%\Superbird\User Data\ %LOCALAPPDATA%\Chedot\User Data\ %LOCALAPPDATA%\Torch\User Data\ GoogleChrome GoogleChrome64 InternetMailRu YandexBrowser ComodoDragon Amigo Orbitum Bromium Chromium Nichrome RockMelt 360Browser Vivaldi Opera GoBrowser Sputnik Kometa Uran QIPSurf Epic Brave CocCoc CentBrowser 7Star ElementsBrowser TorBro Suhba SaferBrowser Mustang Superbird Chedot Torch Login Data Web Data SELECT origin_url, username_value, password_value FROM logins SELECT host_key, name, encrypted_value, value, path, secure, (expires_utc/1000000)-11644473600 FROM cookies SELECT host_key, name, name, value, path, secure, expires_utc FROM cookies SELECT name, value FROM autofill SELECT name_on_card, expiration_month, expiration_year, card_number_encrypted value FROM credit_cards %APPDATA%\Microsoft\Windows\Cookies\ %APPDATA%\Microsoft\Windows\Cookies\Low\ %LOCALAPPDATA%\Microsoft\Windows\INetCache\ %LOCALAPPDATA%\Packages\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\AC\INetCookies\ %LOCALAPPDATA%\Packages\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\AC\#!001\MicrosoftEdge\Cookies\ %LOCALAPPDATA%\Packages\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\AC\#!002\MicrosoftEdge\Cookies\ %LOCALAPPDATA%\Packages\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\AC\MicrosoftEdge\Cookies\ InternetExplorer InternetExplorerLow InternetExplorerINetCache MicrosoftEdge_AC_INetCookies MicrosoftEdge_AC_001 MicrosoftEdge_AC_002 MicrosoftEdge_AC Software\Microsoft\Internet Explorer Software\Microsoft\Internet Explorer\IntelliForms\Storage2 Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook Software\Microsoft\Office\15.0\Outlook\Profiles\Outlook Software\Microsoft\Office\16.0\Outlook\Profiles\Outlook POP3 IMAP SMTP HTTP %appdata%\Waterfox\Profiles\ Waterfox %appdata%\Comodo\IceDragon\Profiles\ IceDragon %appdata%\8pecxstudios\Cyberfox\Profiles\ Cyberfox sqlite3_open sqlite3_close sqlite3_prepare_v2 sqlite3_step sqlite3_column_text sqlite3_column_bytes sqlite3_finalize %APPDATA%\filezilla\recentservers.xml <RecentServers> </RecentServers> <Server> </Server> <Host> </Host> <Port> </Port> <User> </User> <Pass> </Pass> <Pass encoding=”base64″> FileZilla ole32.dll CLSIDFromString {4BF4C442-9B8A-41A0-B380-DD4A704DDB28} {3CCD5499-87A8-4B10-A215-608888DD3B55} vaultcli.dll VaultOpenVault VaultEnumerateItems VaultGetItem MicrosoftEdge Browsers\AutoComplete CookieList.txt SELECT host_key, name, encrypted_value, value, path, is_secure, (expires_utc/1000000)-11644473600 FROM cookies %appdata%\Moonchild Productions\Pale Moon\Profiles\ PaleMoon %appdata%\Electrum\wallets\ \Electrum %appdata%\Electrum-LTC\wallets\ \Electrum-LTC %appdata%\ElectrumG\wallets\ \ElectrumG %appdata%\Electrum-btcp\wallets\ \Electrum-btcp %APPDATA%\Ethereum\keystore\ \Ethereum %APPDATA%\Exodus\ \Exodus \Exodus Eden *.json,*.seco %APPDATA%\Jaxx\Local Storage\ \Jaxx\Local Storage\ %APPDATA%\MultiBitHD\ \MultiBitHD mbhd.wallet.aes,mbhd.checkpoints,mbhd.spvchain,mbhd.yaml .wallet wallets\.wallet wallet.dat wallets\wallet.dat electrum.dat wallets\electrum.dat Software\monero-project\monero-core wallet_path Bitcoin\Bitcoin-Qt BitcoinGold\BitcoinGold-Qt BitCore\BitCore-Qt Litecoin\Litecoin-Qt BitcoinABC\BitcoinABC-Qt %APPDATA%\Exodus Eden\ %Appdata%\Psi+\profiles\ %Appdata%\Psi\profiles\ <roster-cache> </roster-cache> <jid type=”QString”> <password type=”QString”> </password>

Table 3: AZORult Configuration file

The multiple references to Browser Cookies and CryptoWallets confirms the “RuntimeBroker5.exe” sample, initially hidden into the cabilet archive, is an AZORult variant.



Stage 3 – The Payload

The other file download from hairpd[.]com by AZORult’s sample is another executable PE32.



Figure 8: GET request to download the payload.

Hash a75b318eb2ae6678fd15f252d6b33919203262eb59e08ac32928f8bad54ca612 Threat sputik.exe Descrizione Breve Second component downloaded by malware. This component is alive after the infection.

Table 4: Generic information about sputik.exe (Gootkit)

The “sputik.exe” uses a set of evasion techniques to avoid the monitoring of the process, such as invoking the “UuidCreateSequential” API to detect the usage of typical virtual machine’s MAC addresses, but this technique can be easily bypassed by spoofing a real network card one.



Figure 9: Evasion technique through the check “UuidCreateSequential” API call

Bypassing all the evasion techniques reveals the nature of the payload: a Gootkit malware implant.



Figure 10: Command line of the final sample

By instrumenting the execution of the implant, we were able to extract part of the JavaScript code of the malware. The Gootkit implant counts several modules written on top of NodeJS technology embedded into the PE file, revealing part of the implant code.



Figure 11: Portion of Gootkit code snippet

In the past years, Gootkit source code have been leaked online and part of it is also available on the Github platform. This way we were able to investigate differences between the extracted snippets and the known, previously leaked, malware version.



Figure 12: Comparison between extracted Gootkit version and the leaked one

As general consideration, we noticed a lot of similarities between the codes, they are perfectly compatible, but few differences holds. For instance private keys and certificates have been modified, showing the malware author choose a stronger key.

Table 5: Certificate comparison

(New on the left, known/leaked on the right)



Conclusion

These attack waves targeting italian organization and users revealed interesting connections between two threats we was used to monitor and detect across both the InfoSec community and the CERT-Yoroi’s constituency, revealing a hidden link connecting this particular AZORult instance and with the Gootkit implant.

Also, the analysis pointed to an evolution of the dropping techniques used in the initial stages of the attacks by cyber-criminals, showing how the usage of extremely flexible stagers written in high level languages, JavaScript in this case, is becoming more popular and needs to be carefully monitored.

Further details, including Indicators of Compromise (IoCs), are reported in the analysis published on the Yoroi Blog.



Pierluigi Paganini

(SecurityAffairs – AZORult, gootkit)

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