Informations et recherche

Vidar distributed through backdoored Windows 11 downloads and abusing Telegram

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Summary

In April 2022, ThreatLabz discovered several newly registered domains, which were created by a threat actor to spoof the official Microsoft Windows 11 OS download portal. We discovered these domains by monitoring suspicious traffic in our Zscaler cloud. The spoofed sites were created to distribute malicious ISO files which lead to a Vidar infostealer infection on the endpoint. These variants of Vidar malware fetch the C2 configuration from attacker-controlled social media channels hosted on Telegram and Mastodon network.

ThreatLabz believes that the same threat actor is actively leveraging social engineering to impersonate popular legitimate software applications to distribute Vidar malware, as we have also identified an attacker-controlled GitHub repository which hosts several backdoored versions of Adobe Photoshop. These binaries hosted on GitHub, distribute Vidar malware using similar tactics of abusing social media channels for C2 communication.

In this blog, ThreatLabz analyzes the Vidar distribution vector, threat actor correlation, and technical analysis of the binaries involved in this campaign.

 

Key points

  • ThreatLabz discovered several newly registered domains spoofing the official Microsoft Windows 11 OS download portal
  • The spoofed domains were distributing malicious ISO files containing samples of the Vidar infostealer malware
  • The actual C2s used by the malware samples are obtained from attacker-controlled social media channels hosted on Telegram and Mastodon network
  • Using data obtained from this campaign, ThreatLabz was also able to identify another similar one using backdoored versions of Adobe Photoshop

 

Distribution Vector - Windows 11 Theme

The threat actor registered several domains beginning 20th April 2022 that host web pages that masquerade as the official Microsoft Windows 11 download page, which is the latest version of the operating system. ThreatLabz found several other domains registered by this threat actor similar to the one shown below in Figure 1. All of these domains were used to spread malicious ISO files spoofed as a Windows 11 download.

Figure 1

Figure 1: Vidar attacker-controlled domain serving malicious ISO file

The complete list of domains linked to this threat actor that were used in this campaign are mentioned in the Indicators of Compromise (IOC) section.

 

Technical Analysis

ISO file

The binary inside the ISO file is a PE32 binary. The size of the ISO file is very large (more than 300 MB), which helps the attackers evade network security products where there is a file size limitation in place. Example MD5 hashes for this campaign are shown below:

ISO file MD5 hash: 52c47fdda399b011b163812c46ea94a6
PE32 file MD5 hash: 6352540cf679dfec21aff6bd9dee3770

The binary inside the ISO file is digitally signed with a certificate by AVAST. However, this certificate is expired and hence invalid.

Figure 2 shows the details of the certificate and the corresponding serial number.

Figure 2

Figure 2: Details of the certificate used to sign the malicious Vidar binary

All of the binaries in this campaign were signed by a certificate with the same serial number. By pivoting on this serial number, we were able to discover several other malicious binaries from multiple different campaigns and actors, which likely indicates that this is a stolen certificate coming from the AVAST compromise back in 2019.

 

Vidar Samples

The Vidar samples in these campaigns are all packed with Themida (except for the MD5 hash 6ae17cb76cdf097d4dc4fcccfb5abd8a) and over 330MB in size. However, the sample contains a PE file that is only around 3.3MB. Figure 3 shows that the rest of the file content is just artificially filled up with 0x10 bytes to increase the file’s size. The Vidar strings extracted from these samples is provided in the Appendix section at the end of the blog.

Figure 3

Figure 3: Padding of bytes to inflate the Vidar binary size from 3.3MB to 330MB

All of the binaries below are related to the same Windows 11 theme campaign:


MD5: 6352540cf679dfec21aff6bd9dee3770


The Vidar static configuration below contains the embedded parameters needed by the sample to communicate with its C2 and information including the malware version:

  • Profile: 670
  • Profile ID: 739
  • Version: 51.9
  • URL marker: hello
  • URL1: https://t.me/btc20220425
  • Real C2: 195.201.250.209 (Carved out from URL1)
  • URL2: https://ieji.de/@ronxik213
  • Real C2: 107.189.11.124 (Carved out from URL2)

The botnet can be identified by its profile ID. Both of the hardcoded URLs are from social media sites. However, they are used as a dead drop resolver as a first stage. The URL marker instructs Vidar to parse the second stage URL from the social media profiles located at the dead drop resolver.

The following is an example Vidar stealer configuration downloaded from the C2: 1,1,1,1,1,1,1,1,1,1,250,Default;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;

This configuration is the default with every stealing function enabled (passwords, cryptocurrency wallets, two-factor authentication, etc)

The following libraries are downloaded from the C2:

  • update.zip (66cf4ebdceedecd9214caab7ca87908d), which contains the following DLL libraries:
  • freebl3.dll (ef2834ac4ee7d6724f255beaf527e635
  • mozglue.dll (8f73c08a9660691143661bf7332c3c27)
  • msvcp140.dll (109f0f02fd37c84bfc7508d4227d7ed5)
  • nss3.dll (bfac4e3c5908856ba17d41edcd455a51)
  • softokn3.dll (a2ee53de9167bf0d6c019303b7ca84e5
  • sqlite3.dll (e477a96c8f2b18d6b5c27bde49c990bf)  
  • vcruntime140.dll (7587bf9cb4147022cd5681b015183046)

All of these libraries are legitimate that Vidar leverages in order to extract credentials and other data from different applications and browsers.


MD5: da82d43043c101f25633c258f527c9d5
MD5: e9a3562f3851dd2dba27f90b5b2d15c0

Vidar static configuration:

  • Profile: 1281
  • Profile ID: 755
  • Version: 51.9
  • URL marker: hello
  • URL1: 5.252.178.50
  • URL2: https://koyu.space/@ronxik123 
  • Real C2: 107.189.11.124  (Carved out from URL2)

For these samples, the URL1 field in the static configuration is a real C2, and a social media profile is used as a backup URL.

The Vidar stealer configuration downloaded from this C2 was the following: 
1,1,0,1,1,1,1,0,0,1,250,none;

This configuration is customized to extract social media passwords with all of the other Vidar features disabled.

The libraries downloaded from the C2 are the same as the previous sample with the same update.zip (66cf4ebdceedecd9214caab7ca87908d).

 

Distribution Vector - Adobe Photoshop Theme 


ThreatLabz also identified an attacker-controlled GitHub repository which hosts backdoored versions of the application Adobe Photoshop Creative Cloud, which we attribute to the same threat actor. Figure 4 shows the GitHub repository (https://github.com/AdobeInstal) used by the attacker to host a backdoored version of Adobe Photoshop.

Figure 4

Figure 4: Vidar attacker-controlled GitHub repository

 

Technical Analysis

The sample with the MD5 hash below belongs to this Adobe Photoshop theme campaign.


MD5 6ae17cb76cdf097d4dc4fcccfb5abd8a

Vidar static configuration:

  • Profile: 1199
  • Profile ID: 0
  • Version: 51.8
  • URL marker: hello
  • URL1: https://t.me/mm20220428
  • Real C2: 195.201.250.209  (Carved out from URL1)
  • URL2: https://koyu.space/@ronxik123 
  • Real C2: 107.189.11.124 (Carved out from URL2)

The Vidar stealer configuration downloaded from the C2 was the following: 1,1,1,1,1,1,1,1,1,1,250,Default;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;

The libraries downloaded from the C2 are the same as the previous sample with the same update.zip (66cf4ebdceedecd9214caab7ca87908d).

 

Social media abuse for C2 communication

All the binaries involved in this campaign fetch the IP addresses of the C2 servers from attacker-registered social media accounts on the Telegram and Mastodon networks. In the past, the threat actors distributing Vidar have abused other social media networks such as Mastodon. However, the abuse of Telegram is a new tactic that they added to their arsenal.

 

Telegram abuse

In these campaigns, the threat actor created several Telegram channels with the C2 IP address in the channel description. The format used to store the C2 IP address on social media profiles is the following for this campaign: 

<C2_Url_Marker> <C2_IP_address>|

The C2_Url_Marker field in these campaigns was hello. The naming convention for the Telegram channels includes a date that corresponds to the date when these channels were created. As an example, the channel with the handle btc20220425 corresponds to a channel created on April 25, 2022, using btc_stacking as the name as shown in Figure 5.

Figure 5

Figure 5: Vidar attacker-controlled Telegram channel with the C2 IP address included in the channel description

 

Mastodon network abuse

The Mastodon network is a decentralized social network which allows anyone to deploy their own instance of a self-hosted online community. There are several instances of such online communities on the Internet, which are built using Mastodon. Two such instances are ieji[.]de and koyu[.]space. The threat actor created a profile on both of these communities and stored the C2 IP address in the profile section using a format similar to the one used for Telegram channels. Figure 6 and Figure 7 show the profiles created by the threat actor on ieji[.]de and koyu[.]space, respectively.

Figure 6

Figure 6: Vidar attacker-controlled profile on the Mastodon community ieji[.]de with the C2 IP address included in the channel description

Figure 7

Figure 7: Vidar attacker-controlled profile on Mastodon community koyu[.]space with the C2 IP address included in the channel description

 

Conclusion

The threat actors distributing Vidar malware have demonstrated their ability to social engineer victims into installing Vidar stealer using themes related to the latest popular software applications. As always, users should be cautious when downloading software applications from the Internet and download software only from the official vendor websites. The Zscaler ThreatLabZ team will continue to monitor this campaign, as well as others, to help keep our customers safe.

 

Zscaler cloud sandbox detection


Figure 8

Figure 8: Zscaler cloud sandbox detection

In addition to sandbox detections, Zscaler’s multilayered cloud security platform detects indicators at various levels.

Win32.Downloader.Vidar
Win64.Downloader.Vidar

 

Indicators of compromise

Hashes

52c47fdda399b011b163812c46ea94a6
da82d43043c101f25633c258f527c9d5
e9a3562f3851dd2dba27f90b5b2d15c0
6ae17cb76cdf097d4dc4fcccfb5abd8a

 

Domains

ms-win11[.]com
ms-win11.midlandscancer[.]com
win11-serv4[.]com
win11-serv[.]com
win11install[.]com
ms-teams-app[.]net

 

URLs for fetching C2 addresses

https://t.me/btc20220425
https://ieji.de/@ronxik213
https://koyu.space/@ronxik123
https://t.me/mm20220428

 

URLs for fetching ISO files

files.getsnyper[.]com/files/msteams/Setup.iso
files.getsnyper[.]com/files/windows11/Setup.iso
files.getsnyper[.]com/files/msteamsww/Setup.iso

 

Actual C2s

195.201.250.209
107.189.11.124
5.252.178.50
107.189.11.124

 

Appendix


Decoded Strings

Wallets
Plugins
*wallet*.dat
\\Wallets\\
keystore
Ethereum\
\\Ethereum\\
Electrum
\\Electrum\\wallets\\
ElectrumLTC
\\Electrum-LTC\\wallets\\
Exodus
\\Exodus\\
exodus.conf.json
window-state.json
\\Exodus\\exodus.wallet\\
passphrase.json
seed.seco
info.seco
ElectronCash
\\ElectronCash\\wallets\\
default_wallet
MultiDoge
\\MultiDoge\\
multidoge.wallet
JAXX
\\jaxx\\Local Storage\\
file__0.localstorage
Atomic
\\atomic\\Local Storage\\leveldb\\
000003.log
CURRENT
LOCK
LOG
MANIFEST-000001
0000*
Binance
\\Binance\\
app-store.json
Coinomi
\\Coinomi\\Coinomi\\wallets\\
*.wallet
*.config
wallet_path
SOFTWARE\\monero-project\\monero-core
\\Monero\\
SELECT fieldname, value FROM moz_formhistory
\\files\\Soft
\\files\\Soft\\Authy
\\Authy Desktop\\Local Storage\\
\\Authy Desktop\\Local Storage\\*.localstorage
\\Opera Stable\\Local State
INSERT_KEY_HERE
JohnDoe
HAL9TH
api.faceit.com
/core/v1/nicknames/
about
Mozilla/5.0 (iPhone; CPU iPhone OS 6_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A5376e Safari/8536.25
C:\\ProgramData\\
.exe
:Zone.Identifier
[ZoneTransfer] ZoneId=2
Windows
ProgramData
RECYCLE.BIN
Config.Msi
System Volume Information
msdownld.tmp
Recovery
Local\\Temp
Program Files
Recycle.Bin
All Users
MicrosoftEdge\\Cookies
Users\\Public
Local\\Packages
Local\\NuGet
Roaming\\WinRAR
Local\\Microsoft
Microsoft
fee_estimates
peers
mempool
banlist
governance
mncache
mnpayments
netfulfilled
passwords.txt
Login Data
Cookies
Web Data
\\files\\Autofill
\\files\\Cookies
\\files\\CC
\\files\\History
\\files\\Downloads
\\files\\
\\files\\Files
hwid
os
platform
profile
user
cccount
fcount
telegram
ver
vaultcli.dll
VaultOpenVault
VaultCloseVault
VaultEnumerateItems
VaultGetItem
VaultFree
SELECT url FROM moz_places
%s\\Mozilla\\Firefox\\profiles.ini
\\signons.sqlite
SELECT encryptedUsername, encryptedPassword, formSubmitURL FROM moz_logins
\\logins.json
formSubmitURL
usernameField
encryptedUsername
encryptedPassword
guid
SELECT host, name, value FROM moz_cookies
SELECT origin_url, username_value, password_value FROM logins
SELECT name, value FROM autofill
SELECT name_on_card, expiration_month, expiration_year, card_number_encrypted FROM credit_cards
SELECT target_path, tab_url from downloads
SELECT url, title from urls
SELECT HOST_KEY, is_httponly, path, is_secure, (expires_utc/1000000)-11644480800, name, encrypted_value from cookies
C:\\Users\\
\\AppData\\Roaming\\FileZilla\\recentservers.xml
<Host>
<Port>
<User>
<Pass encoding=\
Soft: FileZilla\n
\\AppData\\Roaming\\.purple\\accounts.xml
<protocol>
<name>
<password>
Soft: Pidgin\n
\\Thunderbird\\Profiles\\
C:\\Program Files (x86)\\Mozilla Thunderbird
APPDATA
LOCALAPPDATA
Thunderbird
\\files\\Telegram
\\Telegram Desktop\\tdata\\*
D877F783D5D3EF8C*
\\Telegram Desktop\\tdata\\
key_datas
\\Telegram Desktop\\tdata\\D877F783D5D3EF8C\\*
map*
\\Telegram Desktop\\tdata\\D877F783D5D3EF8C\\
firefox.exe
plugin-container.exe
update_notifier.exe
Mozilla Firefox
\\Mozilla\\Firefox\\Profiles\\
Pale Moon
\\Moonchild Productions\\Pale Moon\\Profiles\\
Waterfox
\\Waterfox\\Profiles\\
Cyberfox
\\8pecxstudios\\Cyberfox\\Profiles\\
BlackHawk
\\NETGATE Technologies\\BlackHawk\\Profiles\\
IceCat
\\Mozilla\\icecat\\Profiles\\
K-Meleon
\\K-Meleon\\
Google Chrome
\\Google\\Chrome\\User Data\\
Chromium
\\Chromium\\User Data\\
Kometa
\\Kometa\\User Data\\
Amigo
\\Amigo\\User Data\\
Torch
\\Torch\\User Data\\
Orbitum
\\Orbitum\\User Data\\
Comodo Dragon
\\Comodo\\Dragon\\User Data\\
Nichrome
\\Nichrome\\User Data\\
Maxthon5
\\Maxthon5\\Users\\
Sputnik
\\Sputnik\\User Data\\
Epic Privacy Browser
\\Epic Privacy Browser\\User Data\\
Vivaldi
\\Vivaldi\\User Data\\
CocCoc
\\CocCoc\\Browser\\User Data\\
URAN
\\uCozMedia\\Uran\\User Data\\
QIP Surf
\\QIP Surf\\User Data\\
Cent Browser
\\CentBrowser\\User Data\\
Elements Browser
\\Elements Browser\\User Data\\
TorBro Browser
\\TorBro\\Profile\\
Suhba Browser
\\Suhba\\User Data\\
Mustang Browser
\\Rafotech\\Mustang\\User Data\\
Chedot Browser
\\Chedot\\User Data\\
Brave_Old
\\brave\\
7Star
\\7Star\\7Star\\User Data\\
Microsoft Edge
\\Microsoft\\Edge\\User Data\\
360 Browser
\\360Browser\\Browser\\User Data\\
QQBrowser
\\Tencent\\QQBrowser\\User Data\\
Opera
\\Opera Software\\Opera Stable\\
OperaGX
\\Opera Software\\Opera GX Stable\\
Local State
Cookies
%s_%s.txt
TRUE
FALSE
\\Microsoft\\Windows\\Cookies\\Low\\
Cookies\\IE_Cookies.txt
\\Packages\\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\\AC\\#!001\\MicrosoftEdge\\Cookies\\
Cookies\\Edge_Cookies.txt
\\files\\Wallets
%USERPROFILE%
%DESKTOP%
KERNEL32.DLL
LoadLibraryA
GetProcAddress
VirtualAllocExNuma
gdi32.dll
ole32.dll
user32.dll
psapi.dll
BCRYPT.DLL
BCryptCloseAlgorithmProvider
BCryptDestroyKey
BCryptOpenAlgorithmProvider
BCryptSetProperty
BCryptGenerateSymmetricKey
BCryptDecrypt
CRYPT32.DLL
CryptUnprotectData
CryptStringToBinaryA
C:\\ProgramData\\nss3.dll
NSS_Init
NSS_Shutdown
PK11_GetInternalKeySlot
PK11_FreeSlot
PK11_Authenticate
PK11SDR_Decrypt
advapi32.dll
RegOpenKeyExA
RegQueryValueExA
RegCloseKey
RegOpenKeyExW
RegGetValueW
RegEnumKeyExA
RegGetValueA
GetUserNameA
GetCurrentHwProfileA
wininet.dll
InternetCloseHandle
InternetReadFile
HttpSendRequestA
HttpOpenRequestA
InternetConnectA
InternetOpenA
HttpAddRequestHeadersA
HttpQueryInfoA
InternetSetFilePointer
InternetOpenUrlA
InternetSetOptionA
DeleteUrlCacheEntry
CreateCompatibleBitmap
SelectObject
BitBlt
DeleteObject
CreateDCA
GetDeviceCaps
CreateCompatibleDC
CoCreateInstance
CoUninitialize
GetDesktopWindow
ReleaseDC
GetKeyboardLayoutList
CharToOemA
GetDC
wsprintfA
EnumDisplayDevicesA
GetSystemMetrics
GetModuleFileNameExA
GetModuleBaseNameA
EnumProcessModules

 

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