Auteur Sujet: [FireEye]Significant FormBook Distribution Campaigns Impacting the U.S. and South Korea  (Lu 282 fois)

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Significant FormBook Distribution Campaigns Impacting the U.S. and South Korea

We observed several high-volume FormBook malware distribution
  campaigns primarily taking aim at Aerospace, Defense Contractor, and
  Manufacturing sectors within the U.S. and South Korea during the past
  few months. The attackers involved in these email campaigns leveraged
  a variety of distribution mechanisms to deliver the information
  stealing FormBook malware, including:

  • PDFs with download links
  • DOC and XLS files with
        malicious macros
  • Archive files (ZIP, RAR, ACE, and ISOs)
        containing EXE payloads


The PDF and DOC/XLS campaigns primarily impacted the United States
  and the Archive campaigns largely impacted the Unites States and South Korea.


FormBook Overview


FormBook is a data stealer and form grabber that has been advertised
  in various hacking forums since early 2016. Figure 1 and Figure 2 show
  the online advertisement for the malware.


 Figure 1: FormBook advertisement


 Figure 2: FormBook underground pricing


The malware injects itself into various processes and installs
  function hooks to log keystrokes, steal clipboard contents, and
  extract data from HTTP sessions. The malware can also execute commands
  from a command and control (C2) server. The commands include
  instructing the malware to download and execute files, start
  processes, shutdown and reboot the system, and steal cookies and local passwords.


One of the malware's most interesting features is that it reads
  Windows’ ntdll.dll module from disk into memory, and calls its
  exported functions directly, rendering user-mode hooking and API
  monitoring mechanisms ineffective. The malware author calls this
  technique "Lagos Island method" (allegedly originating from
  a userland rootkit with this name). 


It also features a persistence method that randomly changes the
  path, filename, file extension, and the registry key used for persistence. 


The malware author does not sell the builder, but only sells the
  panel, and then generates the executable files as a service.




FormBook is a data stealer, but not a full-fledged banker (banking
  malware). It does not currently have any extensions or plug-ins. Its
  capabilities include: 

  • Key logging

  • Clipboard monitoring

  • Grabbing
        HTTP/HTTPS/SPDY/HTTP2 forms and network requests 
  • Grabbing
        passwords from browsers and email clients 

  • Screenshots 


FormBook can receive the following remote commands from the C2 server: 

  • Update bot on host system
  • Download and execute
  • Remove bot from host system
  • Launch a command
        via ShellExecute
  • Clear browser cookies
  • Reboot
  • Shutdown system
  • Collect passwords and create
        a screenshot
  • Download and unpack ZIP archive




The C2 domains typically leverage less widespread, newer generic
  top-level domains (gTLDs) such as .site, .website, .tech, .online, and .info.


The C2 domains used for this recently observed FormBook activity
  have been registered using the WhoisGuard privacy protection service.
  The server infrastructure is hosted on, a Ukrainian
  hosting provider. Each server typically has multiple FormBook panel
  installation locations, which could be indicative of an affiliate model.


Behavior Details


File Characteristics


Our analysis in this blog post is based on the following
  representative sample:







MD5 Hash


Size (bytes)


Compile Time




  Table 1: FormBook sample details




The malware is a self-extracting RAR file that starts an AutoIt
  loader. The AutoIt loader compiles and runs an AutoIt script. The
  script decrypts the FormBook payload file, loads it into memory, and
  then executes it.




The FormBook malware copies itself to a new location. The malware
  first chooses one of the following strings to use as a prefix for its
  installed filename:


ms, win, gdi, mfc, vga, igfx, user, help, config, update, regsvc,
  chkdsk, systray, audiodg, certmgr, autochk, taskhost, colorcpl,
  services, IconCache, ThumbCache, Cookies


It then generates two to five random characters and appends those to
  the chosen string above 


followed by one of the following file extensions:

  • .exe, .com, .scr, .pif, .cmd, .bat


If the malware is running with elevated privileges, it copies itself
  to one of the following directories:

  • %ProgramFiles% 
  • %CommonProgramFiles%


If running with normal privileges, it copies itself to one of the
  following directories:

  • %TEMP%




The malware uses the same aforementioned string list with a random
  string to create a prefix, appends one to five random characters, and
  uses this value as the registry value name.


The malware configures persistence to one of the following two
  locations depending on its privileges:

  • (HKCU|HKLM)\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  • (HKCU|HKLM)\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run




The malware creates two 16-byte mutexes. The first mutex is the
  client identifier (e.g., 8-3503835SZBFHHZ). The second mutex value is
  derived from the C2 information and the username (e.g., LL9PSC56RW7Bx3A5). 


The malware then iterates over a process listing and calculates a
  checksum value of process names (rather than checking the name itself)
  to figure out which process to inject. The malware may inject itself
  into browser processes and explorer.exe. Depending on the target
  process, the malware installs different function hooks (see
    the Function Hooks section for further detail).




The malware uses several techniques to complicate malware analysis: 

  • Timing checks using the RDTSC instruction
  • Calls
        NtQueryInformationProcess with InfoClass=7 (ProcessDebugPort)

  • Sample path and filename checks (sample filename must be shorter
        than 32 characters)
  • Hash-based module blacklist

  • Hash-based process blacklist
  • Hash-based username
  • Before communicating, it checks whether the C2
        server is present in the hosts file


The results of these tests are then placed into a 16-byte array, and
  a SHA1 hash is calculated on the array, which will be later used as
  the decryption key for subsequent strings (e.g. DLL names to load).
  Failed checks may go unnoticed until the sample tries to load the
  supporting DLLs
(kernel32.dll and advapi32.dll).


The correct 16-byte array holding the result of the checks is: 

  • 00 00 01 01 00 00 01 00 01 00 01 00 00 00 00 00 


Having a SHA1 value of:

  • 5b85aaa14f74e7e8adb93b040b0914a10b8b19b2 


After completing all anti-analysis checks, the sample manually maps
  ntdll.dll from disk into memory and uses its exported functions
  directly in the code. All API functions will have a small stub
  function in the code that looks up the address of the API in the
  mapped ntdll.dll using the CRC32 checksum of the API name, and sets up
  the parameters on the stack. 


This will be followed by a direct register call to the mapped
  ntdll.dll module. This makes regular debugger breakpoints on APIs
  inoperable, as execution will never go through the system mapped ntdll.dll.


Process Injection


The sample loops through all the running processes to find
  explorer.exe by the CRC32 checksum of its process name. It then
  injects into explorer.exe using the following API calls (avoiding more
  commonly identifiable techniques such as WriteProcessMemory and CreateRemoteThread):

  • NtMapViewOfSection
  • NtSetContextThread

  • NtQueueUserAPC


The injected code in the hijacked instance of explorer.exe randomly
  selects and launches (as a suspended process) a built-in Windows
  executable from the following list: 

  • svchost.exe, msiexec.exe, wuauclt.exe, lsass.exe, wlanext.exe,
        msg.exe, lsm.exe, dwm.exe, help.exe, chkdsk.exe, cmmon32.exe,
        nbtstat.exe, spoolsv.exe, rdpclip.exe, control.exe, taskhost.exe,
        rundll32.exe, systray.exe, audiodg.exe, wininit.exe, services.exe,
        autochk.exe, autoconv.exe, autofmt.exe, cmstp.exe, colorcpl.exe,
        cscript.exe, explorer.exe, WWAHost.exe, ipconfig.exe, msdt.exe,
        mstsc.exe, NAPSTAT.EXE, netsh.exe, NETSTAT.EXE, raserver.exe,
        wscript.exe, wuapp.exe, cmd.exe 


The original process reads the randomly selected executable from the
  memory of explorer.exe and migrates into this new process via
  NtMapViewOfSection, NtSetContextThread, and NtQueueUserAPC. 


The new process then deletes the original sample and sets up
  persistence (see the Persistence section for more detail). It
  then goes into a loop that constantly enumerates running processes and
  looks for targets based on the CRC32 checksum of the process name. 


Targeted process names include, but are not limited to: 

  • iexplore.exe, firefox.exe, chrome.exe, MicrosoftEdgeCP.exe,
        explorer.exe, opera.exe, safari.exe, torch.exe, maxthon.exe,
        seamonkey.exe, avant.exe, deepnet.exe, k-meleon.exe, citrio.exe,
        coolnovo.exe, coowon.exe, cyberfox.exe, dooble.exe, vivaldi.exe,
        iridium.exe, epic.exe, midori.exe, mustang.exe,
palemoon.exe, qupzilla.exe, sleipnir.exe,
        superbird.exe, outlook.exe, thunderbird.exe, totalcmd.exe


After injecting into any of the target processes, it sets up
  user-mode API hooks based on the process. 


The malware installs different function hooks depending on the
  process. The primary purpose of these function hooks is to log
  keystrokes, steal clipboard data, and extract authentication
  information from browser HTTP sessions. The malware stores data in
  local password log files. The directory name is derived from the C2
  information and the username (the same as the second mutex created above: LL9PSC56RW7Bx3A5). 


However, only eight bytes from this value are used as the directory
  name (e.g., LL9PSC56). Next, the first three characters from the
  derived directory name are used as a prefix for the log file followed
  by the string log. Following this prefix are names corresponding to
  the type of log file. For example, for Internet Explorer passwords,
  the following log file would be created:

  • %APPDATA%\LL9PSC56\LL9logri.ini.


The following are the password log filenames without the prefix:

  • (no name): Keylog data
  • rg.ini: Chrome passwords

  • rf.ini: Firefox passwords
  • rt.ini: Thunderbird
  • ri.ini: Internet Explorer passwords

  • rc.ini: Outlook passwords
  • rv.ini: Windows Vault
  • ro.ini: Opera passwords


One additional file that does not use the .INI file extension is a
  screenshot file:

  • im.jpeg


Function Hooks


Keylog/clipboard monitoring:

  • GetMessageA
  • GetMessageW
  • PeekMessageA

  • PeekMessageW
  • SendMessageA
  • SendMessageW


Browser hooks:

  • PR_Write
  • HttpSendRequestA

  • HttpSendRequestW
  • InternetQueryOptionW

  • EncryptMessage
  • WSASend


The browser hooks look for certain strings in the content of HTTP
  requests and, if a match is found, information about the request is
  extracted. The targeted strings are:

  • pass
  • token
  • email
  • login

  • signin
  • account
  • persistent


Network Communications


The malware communicates with the following C2 server using HTTP requests: 

  • www[.]clicks-track[.]info/list/hx28/




As seen in Figure 3, FormBook sends a beacon request (controlled by
  a timer/counter) using HTTP GET with an "id" parameter in
  the URL.


 Figure 3: FormBook beacon


The decoded "id" parameter is as follows:

  • FBNG:134C0ABB 2.9:Windows 7 Professional x86:VXNlcg==



  • "FBNG" - magic bytes

  • "134C0ABB"
        - the CRC32 checksum of the user's SID 
  • "2.9" -
        the bot version

  • "Windows 7 Professional" –
        operating system version
  • "x86" – operating system

  • "VXNlcg==" - the Base64 encoded
        username (i.e., "User" in this case)


Communication Encryption


The malware sends HTTP requests using hard-coded HTTP header values.
  The HTTP headers shown in Figure 4 are hardcoded.


 Figure 4: Hard-coded HTTP header values


Messages to the C2 server are sent RC4 encrypted and Base64 encoded.
  The malware uses a slightly altered Base64 alphabet, and also uses the
  character "." instead of "=" as the pad character:

  • Standard Alphabet: 

    • ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

  • Modified Alphabet: 

    • ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_



The RC4 key is created using an implementation of the SHA1 hashing
  algorithm with the C2 URL. The standard SHA1 algorithm reverses the
  DWORD endianness at the end of the algorithm. This implementation does
  not, which results in a reverse endian DWORDs. For example, the SHA1
  hash for the aforementioned URL
  is "9b198a3cfa6ff461cc40b754c90740a81559b9ae," but when
  reordering the DWORDs, it produces the correct RC4
  key: 3c8a199b61f46ffa54b740cca84007c9aeb95915. The first DWORD
  "9b198a3c" becomes "3c8a199b."


Figure 5 shows an example HTTP POST request.


 Figure 5: Example HTTP POST request


In this example, the decoded result is: 

  • Clipboard\r\n\r\nBlank Page - Windows Internet


Accepted Commands


When a command is sent by the C2 server, the HTTP response body has
  the format shown in Figure 6.


 Figure 6: FormBook C2 server response
    with command


The data begins with the magic bytes "FBNG," and a
  one-byte command code from hex bytes 31 to 39 (i.e., from
  "1" to "9") in clear text. This is then followed
  by the RC4-encoded command data (where the RC4 key is the same as the
  one used for the request). In the decrypted data, another occurrence
  of the magic FBNG bytes indicates the end of the command data. 


The malware accepts the commands shown in Table 2.



        width="242" valign="top">

Download and execute file from
          %TEMP% directory 



        width="242" valign="top">

Update bot on host machine 






        width="242" valign="top">

Launch a command via











        width="242" valign="top">

Download and unpack ZIP archive into
          %TEMP% directory


          (after decryption)



'1' (0x31) 

'2' (0x32) 

'3' (0x33) 


Remove bot from host machine 

'4' (0x34) 

'5' (0x35) 


Clear browser cookies 

'6' (0x36) 


Reboot operating system 

'7' (0x37) 


Shutdown operating system 

'8' (0x38) 


Collect email/browser passwords and create a

'9' (0x39) 


  Table 2: FormBook accepted commands


Distribution Campaigns


FireEye researchers observed FormBook distributed via email
  campaigns using a variety of different attachments:

  • PDFs with links to the "" URL-shortening
        service, which then redirected to a staging server that contained
        FormBook executable payloads
  • DOC and XLS attachments that
        contained malicious macros that, when enabled, initiated the
        download of FormBook payloads
  • ZIP, RAR, ACE, and ISO
        attachments that contained FormBook executable files


The PDF Campaigns


The PDF campaigns leveraged FedEx and DHL shipping/package delivery
  themes (Figure 7 and Figure 8), as well as a document-sharing theme.
  The PDFs distributed did not contain malicious code, just a link to
  download the FormBook payload.


The staging servers (shown in Table 3) appeared to be compromised websites.


 Figure 7: Example PDF campaign email lure
    with attachment


 Figure 8: Example PDF campaign attachment


Shorted URLs


Staging Servers

















Sample Subject Lines

<Recipient’s_Name> - You have a
          parcel awaiting pick up

          – I shared a file with you









  Table 3: Observed email subjects and download
    URLs for PDF campaign


Based on data from the links, there were a total of
  716 hits across 36 countries. As seen in Figure 9, most of the
  malicious activity from the PDF campaign impacted the United States.


 Figure 9: Geolocation statistics from URL shortener


The DOC/XLS Campaigns


The email campaigns distributing DOC and XLS files relied on the use
  of malicious macros to download the executable payload. When the
  macros are enabled, the download URL retrieves an executable file with
  a PDF extension. Table 4 shows observed email subjects and download
  URLs used in these campaigns.


Staging Server















Sample Subject Lines



ACS PO 1528

          ORDER - PO-074






  Table 4: Observed email subjects and download
    URLs for the DOC/XLS campaign


FireEye detection technologies observed this malicious activity
  between Aug. 11 and Aug. 22, 2017 (Figure 10). Much of the activity
  was observed in the United States (Figure 11), and the most targeted
  industry vertical was Aerospace/Defense Contractors (Figure 12).


 Figure 10: DOC/XLS campaign malicious
    activity by date


 Figure 11: Top 10 countries affected by
    the DOC/XLS campaign


 Figure 12: Top 10 industry verticals
    affected by the DOC/XLS campaign


The Archive Campaign


The Archive campaign delivered a variety of archive formats,
  including ZIP, RAR, ACE, and ISO, and accounted for the highest
  distribution volume. It leveraged a myriad of subject lines that were
  characteristically business related and often regarding payment or
  purchase orders:


Sample Subject Lines


          BCCMKE806868TSC Counterparty:.


Fw: Remittance Confirmation


PO. NO.: 10701 -
          Send Quotaion Pls

Re: bgcqatar project

          August korea ORDER

Purchase Order #234579


purchase order for August017


FireEye detection technologies observed this campaign activity
  between July 18 and Aug. 17, 2017 (Figure 13). Much of the activity
  was observed in South Korea and the United States (Figure 14), with
  the Manufacturing industry vertical being the most impacted (Figure 15).


 Figure 13: Archive campaign malicious
    activity by date


 Figure 14: Top 10 countries affected by
    the Archive campaign


 Figure 15: Top 10 industry verticals
    affected by the Archive campaign 




While FormBook is not unique in either its functionality or
  distribution mechanisms, its relative ease of use, affordable pricing
  structure, and open availability make FormBook an attractive option
  for cyber criminals of varying skill levels. In the last few weeks,
  FormBook was seen downloading other malware families such as NanoCore.
   The credentials and other data harvested by successful FormBook
  infections could be used for additional cyber crime activities
  including, but not limited to: identity theft, continued phishing
  operations, bank fraud and extortion.

Source: Significant FormBook Distribution Campaigns Impacting the U.S. and South Korea