In the third week of March 2018, through FireEye’s Dynamic Threat
Intelligence, FireEye discovered malicious macro-based Microsoft Word
documents distributing SANNY malware to multiple governments
worldwide. Each malicious document lure was crafted in regard to
relevant regional geopolitical issues. FireEye has tracked the SANNY
malware family since 2012 and believes that it is unique to a group
focused on Korean Peninsula issues. This group has consistently
targeted diplomatic entities worldwide, primarily using lure documents
written in English and Russian.
As part of these recently observed attacks, the threat actor has
made significant changes to their usual malware delivery method. The
attack is now carried out in multiple stages, with each stage being
downloaded from the attacker’s server. Command line evasion
techniques, the capability to infect systems running Windows 10, and
use of recent User Account Control (UAC) bypass techniques have also
The following two documents, detailed below, have been observed in
the latest round of attacks:
MD5 hash: c538b2b2628bba25d68ad601e00ad150
Original Filename: РГНФ 2018-2019.doc
The document shown in Figure 1 discusses Eurasian geopolitics as
they relate to China, as well as Russia’s security.
Figure 1: Sample document written in Russian
MD5 hash: 7b0f14d8cd370625aeb8a6af66af28ac
Original Filename: Copy of communication from Security
Council Committee (1718).doc
The document shown in Figure 2 discusses sanctions on humanitarian
operations in the Democratic People’s Republic of Korea (DPRK).
Figure 2: Sample document written in English
In both documents, an embedded macro stores the malicious command
line to be executed in the TextBox property (TextBox1.Text) of the
document. This TextBox property is first accessed by the macro to
execute the command on the system and is then overwritten to delete
evidence of the command line.
Stage 1: BAT File Download
In Stage 1, the macro leverages the legitimate Microsoft Windows
certutil.exe utility to download an encoded Windows Batch (BAT) file
from the following URL: http://more.1apps[.]com/1.txt. The macro then
decodes the encoded file and drops it in the %temp% directory with the
There were a few interesting observations in the command line:
- The macro copies the
Microsoft Windows certutil.exe utility to the %temp% directory with
the name: ct.exe. One of the reasons for this is to evade detection
by security products. Recently, FireEye has observed other threat
actors using certutil.exe for malicious purposes. By renaming
“certutil.exe” before execution, the malware authors are attempting
to evade simple file-name based heuristic detections.
malicious BAT file is stored as the contents of a fake PEM encoded
SSL certificate (with the BEGIN and END markers) on the Stage 1 URL,
as shown in Figure 3. The “certutil.exe” utility is then leveraged
to both strip the BEGIN/END markers and decode the Base64 contents
of the file. FireEye has not previously observed the malware authors
use this technique in past campaigns.
Figure 3: Malicious BAT file stored as an
encoded file to appear as an SSL certificate
BAT File Analysis
Once decoded and executed, the BAT file from Stage 1 will download
an encoded CAB file from the base URL: hxxp://more.1apps[.]com/. The
exact file name downloaded is based on the architecture of the
- For a 32-bit operating
- For a 64-bit
operating system: hxxp://more.1apps[.]com/3.txt
Similarly, based on Windows operating system version and
architecture, the CAB file is installed using different techniques.
For Windows 10, the BAT file uses rundll32 to invoke the appropriate
function from update.dll (component inside setup.cab).
- For a 32-bit operating
system: rundll32 update.dll _EntryPoint@16
- For a 64-bit
operating system: rundll32 update.dll EntryPoint
For other versions of Windows, the CAB file is extracted using the
legitimate Windows Update Standalone Installer (wusa.exe) directly
into the system directory:
The BAT file also checks for the presence of Kaspersky Lab Antivirus
software on the machine. If found, CAB installation is changed
accordingly in an attempt to bypass detection:
Stage 2: CAB File Analysis
As described in the previous section, the BAT file will download the
CAB file based on the architecture of the underlying operating system.
The rest of the malicious activities are performed by the downloaded
The CAB file contains the following components:
- install.bat – BAT file
used to deploy and execute the components.
- ipnet.dll – Main
component that we refer to as SANNY malware.
- ipnet.ini –
Config file used by SANNY malware.
- NTWDBLIB.dll – Performs
UAC bypass on Windows 7 (32-bit and 64-bit).
- update.dll –
Performs UAC bypass on Windows 10.
install.bat will perform the following essential activities:
- Checks the current
execution directory of the BAT file. If it is not the Windows system
directory, then it will first copy the necessary components
(ipnet.dll and ipnet.ini) to the Windows system directory before
- Hijacks a legitimate Windows system service,
COMSysApp (COM+ System Application) by first stopping this service,
and then modifying the appropriate Windows service registry keys to
ensure that the malicious ipnet.dll will be loaded when the
COMSysApp service is started:
- After the hijacked COMSysApp service is
started, it will delete all remaining components of the CAB
ipnet.dll is the main component inside the CAB file that is used for
performing malicious activities. This DLL exports the following two functions:
- ServiceMain – Invoked
when the hijacked system service, COMSysApp, is started.
- Post – Used to perform data exfiltration to the command and
control (C2) server using FTP protocol.
The ServiceMain function first performs a check to see if it is
being run in the context of svchost.exe or rundll32.exe. If it is
being run in the context of svchost.exe, then it will first start the
system service before proceeding with the malicious activities. If it
is being run in the context of rundll32.exe, then it performs the
- Deletes the module
NTWDBLIB.DLL from the disk using the following command:
cmd /c taskkill /im cliconfg.exe /f /t && del /f /q
- Sets the code page on the system
to 65001, which corresponds to UTF-8:
cmd /c REG ADD
HKCU\Console /v CodePage /t REG_DWORD /d 65001 /f
Command and Control (C2) Communication
SANNY malware uses the FTP protocol as the C2 communication channel.
FTP Config File
The FTP configuration information used by SANNY malware is encoded
and stored inside ipnet.ini.
This file is Base64 encoded using the following custom character
Upon decoding the file, the following credentials can be recovered:
- FTP Server:
- Username: cnix_21072852
It then continues to perform the connection to the FTP server
decoded from the aforementioned config file, and sets the current
directory on the FTP server as “htdocs” using the
System Information Collection
For reconnaissance purposes, SANNY malware executes commands on the
system to collect information, which is sent to the C2 server.
System information is gathered from the machine using the following command:
The list of running tasks on the system is gathered by executing the
After successful connection to the FTP server decoded from the
configuration file, the malware searches for a file containing the
substring “to everyone” in the “htdocs” directory. This file will
contain C2 commands to be executed by the malware.
Upon discovery of the file with the “to everyone” substring, the
malware will download the file and then performs actions based on the
following command names:
- chip command: This
command deletes the existing ipnet.ini configuration file from the
file system and creates a new ipnet.ini file with a specified
configuration string. The chip commands allows the attacker to
migrate malware to a new FTP C2 server. The command has the
- pull command: This command is used for the
purpose of data exfiltration. It has the ability to upload an
arbitrary file from the local filesystem to the attacker’s FTP
server. The command has the following syntax:
The uploaded file is compressed and
encrypted using the routine described later in the Compression and
Encoding Data section.
- put command: This command
is used to copy an existing file on the system to a new location and
delete the file from the original location. The command has the
- default command: If the
command begins with the substring “cmd /c”, but it is not followed
by either of the previous commands (chip, pull, and put), then it
directly executes the command on the machine using WinExec.
- /user command: This
command will execute a command on the system as the logged in user.
The command duplicates the access token of “explorer.exe” and spawns
a process using the following steps:
- Enumerates the running processes on the system to search for
the explorer.exe process and obtain the process ID of
- Obtains the access token for the
explorer.exe process with the access flags set to
- Starts the application (defined in the C2
command) on the system by calling the CreateProcessAsUser
function and using the access token obtained in Step 2.
- Enumerates the running processes on the system to search for
Update the FTP server config file
Upload a file from the machine
Copy an existing file to a new destination
Create a new process with explorer.exe access
Execute a program on the machine
Compression and Encoding Data
SANNY malware uses an interesting mechanism for compressing the
contents of data collected from the system and encoding it before
exfiltration. Instead of using an archiving utility, the malware
leverages Shell.Application COM object and calls the CopyHere method
of the IShellDispatch interface to perform compression as follows:
- Creates an empty ZIP file
with the name: temp.zip in the %temp% directory.
- Writes the
first 16 bytes of the PK header to the ZIP file.
- Calls the
CopyHere method of IShellDispatch interface to compress the
collected data and write to temp.zip.
- Reads the contents of
temp.zip to memory.
- Deletes temp.zip from the disk.
- Creates an empty file, post.txt, in the %temp% directory.
- The temp.zip file contents are Base64 encoded (using the same
custom character set mentioned in the previous FTP Config File
section) and written to the file: %temp%\post.txt.
the FtpPutFileW function to write the contents of post.txt to the
remote file with the format: “from
Execution on Windows 7 and User Account Control (UAC) Bypass
NTWDBLIB.dll – This component from the CAB file will be extracted to
the %windir%\system32 directory. After this, the cliconfg command is
executed by the BAT file.
The purpose of this DLL module is to launch the install.bat file.
The file cliconfg.exe is a legitimate Windows binary (SQL Client
Configuration Utility), loads the library NTWDBLIB.dll upon execution.
Placing a malicious copy of NTWDBLIB.dll in the same directory as
cliconfg.exe is a technique known as DLL side-loading, and results in
a UAC bypass.
Execution on Windows 10 and UAC Bypass
Update.dll – This component from the CAB file is used to perform UAC
bypass on Windows 10. As described in the BAT File Analysis section,
if the underlying operating system is Windows 10, then it uses
update.dll to begin the execution of code instead of invoking the
install.bat file directly.
The main actions performed by update.dll are as follows:
- Executes the following
commands to setup the Windows registry for UAC bypass:
- Leverages a UAC
bypass technique that uses the legitimate Windows binary,
fodhelper.exe, to perform the UAC bypass on Windows 10 so that the
install.bat file is executed with elevated privileges:
- Creates an additional BAT file, kill.bat, in
the current directory to delete evidence of the UAC bypass. The BAT
file kills the current process and deletes the components update.dll
and kill.bat from the file system:
This activity shows us that the threat actors using SANNY malware
are evolving their malware delivery methods, notably by incorporating
UAC bypasses and endpoint evasion techniques. By using a multi-stage
attack with a modular architecture, the malware authors increase the
difficulty of reverse engineering and potentially evade security solutions.
Users can protect themselves from such attacks by disabling Office
macros in their settings and practicing vigilance when enabling macros
(especially when prompted) in documents, even if such documents are
from seemingly trusted sources.
Indicators of Compromise
*** This is a Security Bloggers Network syndicated blog from Threat Research Blog authored by Threat Research Blog. Read the original post at: http://www.fireeye.com/blog/threat-research/2018/03/sanny-malware-delivery-method-updated-in-recently-observed-attacks.html