Malware Analysis Report: NotPetya

Hey all, with the recent attacks on Ukraine through the malware WhisperGate peaking my interest, I thought I would try a fun little challenge where I would try to analyze NotPetya, one of the most famous Ukraine Cyberattacks in history and see how far I could go analyzing it alongside writing my first malware analysis report!

My full report with better formatting and my IDA file is available on my github: https://github.com/Adumbrati0n/MalwareReport-NotPetya

Many thanks for reading, feedback is greatly appreciated.

Executive Summary

NotPetya is a malware that was discovered on June 17th 2017. It targeted many Windows Operating Systems using a SMB exploit named ‘Eternal Blue’ originally created by the National Security Agency (NSA). It encrypted data within compromised systems acting similar to a ransomware, displaying messages to send bitcoin for keys to decrypt the data. However, it also destroyed hard disks of such systems so data would be non-recoverable, leading the malware to be known as a form of wiper malware.

This malware analysis report will go over the threat intelligence motivations behind NotPetya, some capabilities that I have deduced from analyzing the malware and at the end of the report, provide recommendations for mitigating and preventing the malware from spreading.

Mitre Att&ck Matrix

Figure 1.1 — MITRE ATT&CK Navigator

Threat intel insights

Targets

The malware has spread and infected numerous systems around the globe mainly in the countries of Ukraine, Russia and East Europe. The majority of its infections are however situated in Ukraine, affecting multiple Ukrainian businesses, state-enterprises, banks, transport and metro systems.

Figure 2.1 — Percentage of NotPetya Infections per country

Motivations

The threat actors created an initial infection vector through the exploitation of an update procedure for a third-party Ukrainian software product named ‘MEDoc’. MEDoc is a software mainly used for tax accounting purposes in multiple Ukrainian businesses and government, financial and energy sectors. We can safely say that the main motivation of the threat actors were to disrupt, hinder and sabotage multiple Ukrainian organizations and infrastructure to harm Ukraine’s economy.

Attributions

The US government has attributed NotPetya to APT Sandworm, a Russian-tied intelligence and cyber warfare group funded by the Russian Intelligence Directorate (GRU). Ukraine has been in conflict with Russia for a long time due to political trade deals with the European Union and from the Russian annexation of Crimea from Ukraine starting in 2014.

Technical Analysis

Main Malware

The malicious sample, not_petya.exe acts as the main malware through a compromised update of the tax accounting software ‘MEDoc’ used by many Ukraine organisations. It has a multitude of features after the initial infection vector including privilege escalation, network enumeration and propagation, encryption and MBR overwrite, forced system-shutdown and performing anti-analysis techniques to make the malware harder to detect and analyze.

Exploits/Vulnerabilities and lateral movement

The malware exploits the following vulnerabilities CVE-2017–0144 and CVE-2017–0145 also known as ‘Eternal Blue’ and ‘Eternal Romance’. These CVE’s both exploit Microsoft’s implementation of the SMBv1 protocol enabling a threat actor to generate SMBv1 packets to trigger the vulnerability and allow the execution of arbitrary code, spreading to unpatched machines and networks.

The Eternal Blue vulnerability allows an inter-process communication share (IPC$) to perform a null session connection by default. This special share is created by the Windows Server Service and allows the connection to be established by anonymous users/login. NotPetya exploits this vulnerability allowing SMB packets over TCP connection to open the null session in the IPC$ share allowing threat actors to perform network enumeration and to propagate the malware.

Figure 3.1 — IPC$ Functionality seen within NotPetya

Privilege escalation

The malware first attempts to find and store how long it has been since the system has started in milliseconds via the GetTickCount API. The malware then tries to gain more privileges within the operating system through the following table:

Figure 4.1 — Showcasing GetTickCount, SeShutdownPrivilege, SeDebugPrivilege

It rewrites the DesiredAccess to TOKEN_ADJUST_PRIVILEGES for these privileges via the API’s OpenProcessToken, LookupPrivilegeValueW, AdjustTokenPrivileges.

Figure 4.2 — Showcasing DesiredAccess = TOKEN_ADJUST_PRIVILEGES

Once the malware gains all privileges, it is able to propagate more of its functions via the SMB Eternal Blue exploit, force shutdown and reboot the infected machine via the SeShutdownPrivilege level and encrypt and overwrite data in hard-drives making them unusable via SeDebugPrivilege and SeTcbPrivilege.

Network enumeration

The malware attempts to gather network and computer information on an infected machine such as IP addresses, subnet-masks, computer name and computer version by creating a thread via the CreateThread API and executing it to see if the malware can connect to SMB port 445.

Interesting API’s invoked by the malware that allow network enumeration are as follows:

Figure 5.1 — Showcasing IP, Subnet mask Collection

If the malware is able to gather information about a machine or server, it will use DHCP for enumeration to get the IP addresses of infected machines and uses SMB from the Eternal Blue exploit to connect to more hosts.

It does this through the following API’s:

Figure 5.2 — Showcasing DhcpEnumSubnets, DhcpGetSubnetInfo

Resources analysis and examination

Notpetya contains several resources which we can extract via Resource-Hacker. A table of the resources can be seen below:

The malware checks if the infected machine is a 32-bit or 64-bit system via IsWow64Process. If the machine is 32-bit the malware will use Resource 1, if it is 64-bit the malware will use Resource 2. It will unlock the RT_RCDATA in memory and creates a new file [x].tmp in the Appdata %Temp% Path.

Example: C:\Users\User\Appdata\Local\Temp\D0A6.tmp

Figure 6.1 — Showcasing creation of new .tmp file and GUID

The malware will then create a unique GUID for the [x].tmp File and writes the resource to it, executing the resource as a new process with the argument \\.\pipe\{GUID} to obtain user credentials. Once complete, the malware will delete the [x].tmp file by calling to the API DeleteFileW.

The malware also uses Resource 3 in another function, unlocking the RT_RCDATA in memory and writes the resource to a new file called dllhost.dat in the C:\Windows path.

Figure 6.2 — Resource 3 Dllhost.dat creation

Resource 4 is a resource used to exploit the EternalBlue vulnerability via SMB.

Figure 6.3 — Resource4 SMB Payload

Remote execution

The malware uses the following command for remote execution on the infected machine:

WMIC or the Windows Management Instrumentation Command-Line is also used for remote execution on the infected machine. It uses a username and password combination to spread to other machines via stolen credentials or user token impersonation.

Encryption algorithms

Algorithms used: RSA and AES

RSA is an asymmetric algorithm using public and private keys for encryption and decryption. AES is different from RSA as it is a symmetric algorithm and uses one key for encryption and decryption.

The malware first uses the Microsoft Enhanced RSA and AES Cryptographic Provider to generate an AES-128 bit key to encrypt all the files within an infected machine via the API CryptGenKey.

It searches for files to encrypt with the following file name extensions using the generated AES key to encrypt the files:

The malware also imports the RSA-2048 public key of the threat actor via the API CryptImportKey which is stored in the malware: MIIBCgKCAQEAxP/VqKc0yLe9JhVqFMQGwUITO6WpXWnKSNQAYT0O65Cr8PjIQInTeHkXEjfO2n2JmURWV/uHB0ZrlQ/wcYJBwLhQ9EqJ3iDqmN19Oo7NtyEUmbYmopcq+YLIBZzQ2ZTK0A2DtX4GRKxEEFLCy7vP12EYOPXknVy/+mf0JFWixz29QiTf5oLu15wVLONCuEibGaNNpgq+CXsPwfITDbDDmdrRIiUEUw6o3pt5pNOskfOJbMan2TZu6zfhzuts7KafP5UA8/0Hmf5K3/F9Mf9SE68EZjK+cIiFlKeWndP0XfRCYXI9AJYCeaOu7CXF6U0AVNnNjvLeOn42LHFUK4o6JwIDAQAB

After, the AES-generated key is exported via the API CryptExportKey for each machine. The AES-generated key is then encrypted with the threat actors’ RSA embedded public key.

When files within the infected machine are encrypted, the malware will drop a file called ‘README.txt’ and writes a ransom note within it. It will also include the AES generated key encrypted with the threat actors RSA-2048 key as the personal installation key for that specific machine. The malware will then use the API CryptDestroyKey releasing the handle for the AES-128 key so it cannot be used again, making decryption of files impossible as we also do not have the private key of the threat actor to decrypt the AES-128 generated key.

Figure 7.1 — NotPetya Imports RSA-2048 public key and encrypts AES-128 key with the public key
Figure 7.2 — NotPetya releasing handle of AES-128 key
Figure 7.3 — README.txt Ransom Note

Destroying the master boot record

The malware gets the system directory and opens the C volume on the physical drive, calling to the API DeviceIOControl with the IoControlCode IOCTL_VOLUME_GET_VOLUME_DISK_CONTENTS to gather information of the location of the volume driver.

Figure 7.4 — Get System Directory, Open C Volume

It will then attempt to read the partition information such as type, size and nature of the physical disk via the IOControlCode IOCTL_DISK_GET_PARTITION_INFO_EX from another call to the API DEVICEIOControl.

Figure 7.5 — Read Partition Information

To modify the MBR it will start calling to a function with the API’s CryptAcquireContextA to handle the cryptographic service provider and CryptGenRandom to write an array of random bytes to read/write sectors within the disk.

The malware then tries to overwrite and modify certain sectors within the Master Boot Record by using the API DeviceIoControl with the IoControlCode IOCTL_DISK_GET_DRIVE_GEOMETRY to control the volume driver and creates a file named PhysicalDrive0, writing bytes within it to destroy the Master Boot Record and make it unrepairable. Once completed, the malware also uses the IoControlCode FSCTL_DISMOUNT_VOLUME to dismount the volume after modifying the Master Boot Record.

Figure 7.6 — Modify MBR and Dismount Volume

Forced System Shutdown and Anti-Analysis

Forced system shutdown

The malware gets the current time and version of an infected machine via the API’s GetLocalTime and GetTickCount. It will use the following command via cmd.exe to schedule a system shutdown/reboot of up to 60 minutes from the current time the malware was executed on the machine:

Figure 8.1 — Showcasing the schtasks command in Ollydbg

Anti-Analysis

The malware also tries to make it harder for analysts and users to find out what is happening on an infected machine by clearing event logs before a forceful shutdown/reboot process. It uses the following command via cmd.exe to clear the logs within the system:

Anti-reversing techniques

Anti-Antivirus checking

Notpetya has a form of anti-virus checking, examining anti-virus software within a system. If any of these processes are found, certain functionality of the malware such as encryption or network propagation via the SMB EternalBlue exploit may not occur.

The malware first takes a snapshot of all current processes and threads within a system via the API CreateToolhelp32Snapshot with the dwFlags parameter being TH32CS_SNAPALL. It will search for antivirus processes via the API’s Process32FirstW and Process32NextW until it finds an AV executable. If none of the AV executables are found, the malware will run normally.

The Antivirus software that NotPetya checks are seen in the table below:

Figure 9.1 — NotPetya Checks the following AV products

Recommended Actions

There are a multitude of ways we can prevent and mitigate NotPetya from spreading to other networks and machines.

· Install the Windows Security Update and patch MS17–010 which fixes both the Eternal Blue and Eternal Romance vulnerabilities

· Disable SMBv1 if your machine currently does not need to use it.

· Have an antivirus/anti-malware solution which can help prevent malicious executables from executing

· Implement a firewall rule to block SMB traffic on port 445

· If you are in a large organization, backup your data or implement a DRP (Disaster Recovery Plan) or disaster recovery sites (Cold, Warm, Hot sites) in order to backup and restore data when needed.

Conclusion

NotPetya is a malicious malware that is incredibly complex and was used to successfully target multiple Ukrainian organisations and businesses.

It tries to gain higher privileges within an infected hosts system scanning for user credentials and network information. It uses network propagation to spread to other hosts via the Eternal Blue and Eternal Romance SMB vulnerabilities. Furthermore, it uses encryption algorithms to encrypt data within drives, but also overwrites the master boot record to make system recovery nigh impossible. NotPetya as a result, is a form of wiper malware masking itself as a type of ransomware.

I hope you enjoyed reading this report. Feedback is greatly appreciated.

Yara Signature

rule Notpetya

{

meta:

description = “Yara Rule for Notpetya”

author = “Ben Lee”

date = “2022–23–01”

hash = “71b6a493388e7d0b40c83ce903bc6b04”

strings:

$s1 = “CryptDestroyKey” fullword ascii

$s2 = “wowsmith123456@posteo.net”

$s3 = “.3ds.7z.accdb.ai.asp.aspx.avhd.back.bak.c.cfg.conf.cpp.cs.ctl.dbf.disk.djvu.doc.docx.dwg.eml.fdb.gz.h.hdd.kdbx.mail.mdb.msg.nrg.ora.ost.ova.ovf.pdf.php.pmf.ppt.pptx.pst.pvi.py.pyc.rar.rtf.sln.sql.tar.vbox.vbs.vcb.vdi.vfd.vmc.vmdk.vmsd.vmx.vsdx.vsv.work.xls.xlsx.xvd.zip.” fullword wide

$s4 = “MIIBCgKCAQEAxP/VqKc0yLe9JhVqFMQGwUITO6WpXWnKSNQAYT0O65Cr8PjIQInTeHkXEjfO2n2JmURWV/uHB0ZrlQ/wcYJBwLhQ9EqJ3iDqmN19Oo7NtyEUmbYmopcq+YLIBZzQ2ZTK0A2DtX4GRKxEEFLCy7vP12EYOPXknVy/+mf0JFWixz29QiTf5oLu15wVLONCuEibGaNNpgq+CXsPwfITDbDDmdrRIiUEUw6o3pt5pNOskfOJbMan2TZu6zfhzuts7KafP5UA8/0Hmf5K3/F9Mf9SE68EZjK+cIiFlKeWndP0XfRCYXI9AJYCeaOu7CXF6U0AVNnNjvLeOn42LHFUK4o6JwIDAQAB” fullword wide

$s5 = “1Mz7153HMuxXTuR2R1t78mGSdzaAtNbBWX” fullword ascii

$s6 = “Send your Bitcoin wallet ID and personal installation key to e-mail” fullword wide

condition:

(uint16(0) == 0x5a4d) and (filesize< 400000) and (all of them)

}

References

· https://www.justice.gov/opa/press-release/file/1328521/download

· https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-0144

· https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-0145

· https://blog.3or.de/reverse-engineering-nopetyawiper-pt-1.html

· https://docs.microsoft.com/en-us/troubleshoot/windows- server/networking/inter-process-communication-share-null-session#:~:text=KB%20number%3A%203034016-,About%20IPC%24%20share,domain%20accounts%20and%20network%20shares.&text=Then%20it%20makes%20sure%20that,the%20specified%20users%20or%20groups.

· https://attack.mitre.org

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Ben Lee

I focus on Malware, RE, DFIR. This blog is used to improve my understanding of these concepts and show my progress.