Updated on March 12th, 2020: to reflect that Microsoft has now made a patch for the vulnerability available. As such, we’ve updated the advisory reflects updated mitigations.
On March 10th, a critical Remote Code Execution (RCE) vulnerability in the Microsoft Server Message Block (SMBv3) protocol was inadvertently disclosed. The vulnerability, known as CVE-2020-0796, is caused by how newer Windows operating systems handle certain requests, specifically compressed SMBv3 packets. Microsoft intended to release a patch for this vulnerability as part of March’s “Patch Tuesday”, however, the patch appears to have been pulled at the last minute. This led to the inadvertent disclosure of the issue before a patch is available. The flaw, considered critical, and could allow attackers to execute arbitrary code without user interaction and without authentication.
This critical vulnerability is considered “wormable” as it leads to pre-authenticated remote code execution of the Windows server implementation of SMBv3. To exploit the vulnerability on a Windows machine acting as an “SMB server”, unauthenticated attackers can simply send a maliciously crafted packet to a targeted SMBv3 Server. Once an attacker has successfully compromised one system, they can attempt to automatically exploit other reachable SMB servers. However, to exploit an SMB Client, an unauthenticated attacker would need to configure a malicious SMBv3 server and convince a user to connect to it.
The Windows implementation of the SMB protocol was recently exploited by WannaCry, NotPetya and other recent attacks, enabled by a leak of reliable equation group exploits in 2017. However, Due to the difficulty in successfully and reliably exploiting such vulnerabilities, the Cyber Fusion Center does not expect to see immediate mass exploitation attempts. There are currently no publicly available exploits targeting this vulnerability and there are several Microsoft Windows exploit mitigations that make building a successful and reliable exploit very difficult.
While they are no current public exploits, the Cyber Fusion Center strongly recommends mitigating the vulnerability as soon as possible.
Note: On March 12, 2020, Microsoft released an out-of-band patch for this vulnerability. The Cyber Fusion Center strongly recommends that organizations apply the patch as soon as possible, especially on SMB servers such as Active Directory domain controllers and file shares. If it’s not possible to patch in the very near future, the Cyber Fusion Center recommends disabling compression for the SMBv3 protocol with the commands in the “Temporary Mitigations” section of this advisory.
- Microsoft Windows 10 Version 1903 (May 2019 update)
- Microsoft Windows 10 Version 1909 (v1909)
- Microsoft Windows Server Version 1903 (Server Core Installation)
- Microsoft Windows Server Version 1909 (Server Core Installation)
Attackers who successfully exploit this vulnerability can execute arbitrary code within the context of the SMBv3 process. The vulnerability is considered “wormable” as it allows for pre-authenticated remote code execution without any user interaction.
On March 12th, 2020 (one day after “Patch Tuesday”) Microsoft released out-of-band patches for this severe vulnerability in Window’s implementation of SMBv3 compression. The Cyber Fusion Center strongly recommends organizations apply this patch rather than use the temporary mitigations outlined below.
The patch is available via the traditional Microsoft Update delivery process and on the Microsoft Security Response Centers website.
While there is no patch for this vulnerability yet, it’s possible to mitigate the issue on SMB servers by disabling support for compression on the SMBv3 protocol.
Windows administrators can disable compression to prevent unauthenticated attackers from exploiting the vulnerability on SMBv3 Servers by using the PowerShell command below.
Set-ItemProperty -Path “HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters” DisableCompression -Type DWORD -Value 1 -Force
- No reboot Is required after making this change
- This workaround does not prevent exploitation of SMB clients
If necessary, you can rollback this change with the Powershell command bellow:
Set-ItemProperty -Path “HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters” DisableCompression -Type DWORD -Value 0 -Force
The Cyber Fusion Center also strongly recommends that organizations mitigate the potential of an attack on a Windows 10 client by blocking all outbound SMB (TCP port 445) on corporate firewalls.
Additionally, Microsoft has published guidelines for preventing lateral SMB connections and preventing SMB traffic from entering or leaving the corporate network provides details on how to mitigate this vulnerability and other attackers in the future:
On January 14th, 2020 (Patch Tuesday), Microsoft released patches for a severe vulnerability Window’s cryptographic subsystems and critical vulnerabilities in Windows Server Remote Desktop (RDP) Gateway. These Microsoft vulnerabilities are considered critical and the Cyber Fusion Center strongly recommends applying these patches as soon as possible. Kudelski Security expects active exploitation in the near future.
The U.S National Security Agency released an advisory regarding a vulnerability in a cryptographic library (Crypt32.dll) used in Microsoft Windows 10, Windows Server 2016, and Windows Server 2019 (CVE-2020-0601). This issue impacts the verification of elliptic curve cryptography (ECC) signatures in security certificates. The verification of such certificates has been discovered to be defective and may allow an attacker to incorrectly validate a forged certificate. Successful exploitation of this issue has been shown to allow for interception, modification, and decryption of TLS / HTTP(s) traffic by attackers in privileged network positions. Additionally, this may allow attackers to successfully bypass code-signing requirements on Windows systems or bypass Device Guard application whitelisting solutions.
Kudelski Security’s research team has been able to successfully exploit this vulnerability to issue spoofed HTTPs certificates considered valid by Windows 10, Windows Server 2016, and Windows Server 2019:
Additionally, Kudelski Security has released a public POC available on our Github page:
This “Patch Tuesday” also included patches for multiple critical vulnerabilities in Windows Remote Desktop (RDP) Gateways. These critical vulnerabilities lead to unauthenticated Remote Code Execution (RCE) with SYSTEM privileges. Such vulnerabilities could be leveraged by attackers to remotely compromise systems without authentication or user interaction. Remote Desktop Gateways allow organizations to centralize Remote Desktop services and provide remote access to Windows endpoints and servers without a VPN, provide web-based RDP user experiences, and more.
Microsoft released patches for a severe vulnerability Window’s cryptographic subsystems and critical vulnerabilities in Windows Server Remote Desktop (RDP) Gateway. Kudelski Security expects active exploitation in the near future. As such, the Cyber Fusion Center strongly recommends mitigating these issues as soon as possible.
The Microsoft Windows cryptographic subsystem vulnerability was publicly disclosed jointly by Microsoft and the U.S National Security Agency (NSA) after being successfully patched by Microsoft. Microsoft and the NSA have publicly stated that that they’ve not observed any exploitation of this vulnerability. Additionally, Kudelski Security has been able to leverage this vulnerability to successfully to issue spoofed HTTPs certificates considered valid by Windows 10, Windows Server 2016, and Windows Server 2019 and has released public Proof Of Concept code (POC) on our github page. Please review the sources linked in this document for our blog post and links to the POC code.
The vulnerability is in a cryptographic library (Crypt32.dll) used in Microsoft Windows 10, Windows Server 2016, and Windows Server 2019 (CVE-2020-0601). This issue impacts the verification of elliptic curve cryptography (ECC) signatures in security certificates. The verification of such certificates has been discovered to be defective and may allow an attacker to incorrectly validate a forged certificate. Successful exploitation of this issue has been shown to allow for interception, modification, and decryption of TLS / HTTP(s) traffic by attackers in privileged network positions. Additionally, this may allow attackers to successfully bypass code-signing requirements on Windows systems or bypass Windows Device Guard or other application whitelisting solutions.
Additionally, Microsoft has released patches for multiple critical vulnerabilities in Windows Remote Desktop (RDP) Gateways. These critical vulnerabilities may lead to unauthenticated Remote Code Execution (RCE) with SYSTEM privileges. These vulnerabilities could be leveraged by attackers to remotely compromise systems without requiring to validate credentials or user interaction. Remote Desktop Gateways allow organizations to centralize Remote Desktop services and provide remote access to Windows endpoints and servers without a VPN, provide web-based RDP user experiences, and more.
It’s important to note that Remote Desktop (RD) Gateway is a separate application rather traditional Remote Desktop Protocol. Organizations looking to identify any potentially exposed RD gateways should look for systems exposing UDP port 3391 (not the traditional RDP Port on TCP 3389) along with Remote Desktop Web Services on HTTPs (TCP/443).
Kudelski Security expects to see attackers leveraging these Remote Desktop Gateway vulnerabilities to compromise unpatched systems in the near future due to the prevalence of the technology and the ability to compromise critical systems without authentication or user interaction. As such, we strongly recommend that clients apply these patches as quickly as possible.
Microsoft Windows Crypto Subsystem issue
Organizations who do not currently have Kudelski Security Cyber Fusion Center’s Threat Monitoring and Hunting services may want to ensure Windows Application Logs are being centrally collected and monitored. Microsoft has introduced a new Windows Event source named “Microsoft-Windows-Audit-CVE”. Microsoft Windows will now write events to the local Windows application logs with this source if there are attempts to exploit this vulnerability. Note that the Windows Event source will only be available after the latest patches have been applied.
Additionally, it’s possible to detect potentially invalid TLS certificates being used to exploit this vulnerability by intercepting TLS packets and checking certificate signature for uncommon elliptic curve parameters. By analyzing TLS traffic, the “ServerHello/Certificate/ServerHelloDone” packet contains the certificate which should be checked for possible forgery.
Additionally, the Cyber Fusion Center is actively working with our vendor partners to ensure we can actively detect attempted exploitation of this vulnerability. For customers with the Cyber Fusion Center’s Endpoint Detection and Response service will be proactive notified if potential exploitation is detected.
Microsoft Remote Desktop Gateway issues
Organizations who do not currently have Kudelski Security Cyber Fusion Center’s Threat Monitoring and Hunting services or our vulnerability scanning services may want to identify exposed versions of Web Services for remote desktop or systems that respond to UDP port 3391. Several vendors have released IDS or IPS detection signatures.
Additionally, the Cyber Fusion Center is actively working with our vendor partners to ensure we can actively detect attempted exploitation of these vulnerabilities. For customers with the Cyber Fusion Center’s Endpoint Detection and Response service will be proactive notified if potential exploitation is detected.
Mitigation and Response
The Cyber Fusion Center is actively working with our vendor partners to ensure we can actively detect attempted exploitation of these vulnerabilities. For customers with the Cyber Fusion Center’s Endpoint Detection and Response or Threat Monitoring services will be proactive notified if potential exploitation is detected.
For customers with the Cyber Fusion Center’s vulnerability scanning service will be proactively notified if any vulnerable Remote Desktop gateway systems are detected.
wCry2 Ransomware spreading via EternalBlue (MS17-010)
Update May 15
Mid-morning (U.S time) Neel Mehta, a security researcher at Google, posted a cryptic tweet with the hashtag “#WannaCryptAttribution”:
The tweet referenced hashes of two examples, one of the current WannaCrypt ransomware campaign, and a sample linked to the Lazarus ATP group from February 2015. Breaches and operations conducted by the Lazarus group, including the Sony wiper attack, had previously been attributed to the government of North Korea (DPRK).
Researchers have reviewed the locations in the binaries mentioned by Neel and identified that both samples share the same code, have similar functions, and very similar modules in several locations. As such, many security researches have attributed the WannaCrypt ransomware campaign to the DPRK. Kudelski Security urges caution when attempting attribution based on similarities in binaries as several state sponsored threat actors often repurpose code in other to obfuscate the true origin of malware and tools.
A word about the Bitcoin wallets used
The Kudelski Security Cyber Fusion Center has continued to monitor the three bitcoin wallets found the various WannaCrypt samples. As of the time of this writing, the three wallets have received a total of 34.9 Bitcoins ($61,153.77 USD at current exchange rates) from 232 unique transactions. That is a large increase from the $27,614 USD observed early this morning.
It is likely that as organizations and users arrived at work this morning, several have chosen to pay the ransom in an attempt to restore access to critical files:
Over the weekend and throughout Monday morning and afternoon Kudelski Security has continued to monitor developments related to the Wana Decrypt0r 2.0 / WannaCrypt ransomware. Since our last update, we’ve seen at least two new variants of the ransomware which include new “kill switch” domains. Luckily, these new samples have been quickly identified and the additional domains have been registered, thus stopping the spread of these new variants.
Over the weekend the Kudelski Security Cyber Fusion Center team examined available WannaCrypt examples and discovered that both the “worm code” and the portions of the malware which deploy the actual ransomware payload are highly modular. The modular nature of these variants means that we can expect to see modified examples that attempt to deploy other ransomware or malware variants. Additionally, the worming code can easily be replaced to leverage other remote code execution (RCE) vulnerabilities as they become available.
Windows 10 not affected
Analysis by Microsoft, Kudelski Security, and several other organizations has also identified that the EternalBlue exploit code leveraged by currently available examples of the WannaCrypt ransomware appear to only target the Windows 7 and Windows Server 2008 (or earlier) platforms. As such, organizations or users with Windows 10 were not affected by this attack.
Decryption is a manual process
Independent security researchers investigating samples of the WannaCrypt ransomware have discovered that the ransomware requires manual intervention from “operators” to provide the decryption keys. Additionally, there has not yet been any independent verification that paying the ransom actually ensures that files are decrypted. Kudelski Security recommends that affected organizations do not pay the ransom.
Initial infection vector still unknown
The initial infection vector that caused the start of the campaign in Europe is still unknown. While most ransomware campaigns spread by either phishing campaigns or by leveraging exploit kits. However, in this case researchers have not yet identified any email examples or exploit kit landing pages which distribute to the WannaCrypt` variants which such havoc over the last 3 days.
Update May 13
Data was coming in very quickly on Friday and while we worked to provide timely and reasonable information we know now more about what happened and how the Wana Decrypt0r 2.0 ransomware outbreak managed to escalate so quickly.
First some good news: The malware, once executed checked for the existence of a randomly generated domain. If the domain did not exist or could not be reached, the execution of malicious code continued. If the domain existed and was accessible, a kill switch was activated and the infection was halted. A malware blogger and reverse engineer from the U.K registered the domain which effectively slowed the malware spread in the U.S. Unfortunately, many anti-virus vendors began to block the domain, unintentionally allowing the installation to continue, realizing the error some of the anti-virus vendors have removed the block and now sinkhole the domain instead.
More information here:
The unfortunate news is that there are now samples emerging that no longer contain the domain based “kill switch”.
An example of this new variant is available here:
Additionally, are further review of the malicious binaries, we’ve identified that all RF1918 (private) netblocks as well as randomly generated internet netblocks are also scanned looking for further propagation avenues. This means that organizations could also potentially be affected by way of site-to-site VPN connection with business partners or vendors. The ransomware has also spread via guest wifi, thus users should be cautious as it is possible they could be affected while connected to an open wifi hotspot.
Researchers have noted that WannaCry 2.0 is not the actual worm. The worm is the MS17-010 “spreader”. WannaCry 2.0 is dropped by the “spreader” which can also be used to drop other binaries and files. Thus, it is extremely critical that organizations apply the MS17-010 patches as quickly as possible.
Mac OS and Linux users running Windows VMs or Wine are also affected if not patched.
Along with the ETERNALBLUE components, the dropper also calls out and downloads DOUBLEPULSAR. Organizations affected will want to check for the existence of DOUBLEPULSAR once the initial attack is remediated. There is a free script available to check for this located here:
The Wana Decrypt0r 2.0 ransomware campaign utilized 3 Bitcoin wallets and as of today they show modest returns. Note: there is no indication that paying the ransom actually provided the user with the keys to decrypt their data and some researchers reported that users had to interact with a human via phone or web chat to negotiate. In the ransom note, the attackers mention that if someone is “too poor” to pay that their files will automatically decrypt in 6 months.
The following Bitcoin wallets have been linked to this ransomware campaign:
The Global response to this campaign has been swift and effective, unfortunately, too late for a large number of European organizations. Microsoft released updates to its malware protection engine to block the malware. Additionally, Microsoft has unexpectedly released security patches for EternalBlue and MS17-010 vulnerabilities for the unsupported Windows XP, Vista, Windows 8, and Windows server 2013 operating systems.
When unfortunate events like this take place, it’s easy for information security practitioners to point fingers and assign blame but the global information security community would be better served by helping organizations understand and avoid these situations in the future.
Moving forward, Kudelski Security expects to see most if not all ransomware and malware families using similar techniques to spread quickly and infect large numbers of users and organizations.
This global ransomware outbreak is a stark reminder that organizations must have the basics covered. Organizations must review and evaluate their vulnerability and patch management programs to ensure confidence, comprehensiveness, and effectiveness. Security patches are a fundamental and critical foundation of any organizations security program and should be tested and applied quickly. Organizations should also perform a “health checkup” and review backup strategies, test backups regularly, and ensure backups are easily accessible while also being protected from encryption and deletion. Also, organizations should review and reevaluate what traffic is allowed to and from the internet.
Once the basics are covered, now is the time to start looking at some of the newer endpoint protection platforms that rely on behavioral indicators that executables could be malicious instead of solely relying on signatures.
Now is the time to take a look at security, review and apply the basics, and then pragmatically strengthen its effectiveness.
On May 12 2017, a widespread cyber-attack utilizing the WCry2 ransomware, also known as Wana Decrypt0r 2.0, began spreading across the globe. At the time of this writing, the Ransomware has currently impacted organizations in 99 countries and continues to spread. Wana Decrypt0r 2.0 uses the EternalBlue exploit (MS17-010), released by the Shadow Brokers in March 2017. This SMB exploit is used to attempt to infect other machines within the same network and to scan for, and infect, potentially vulnerable Windows machines on the internet.
Wana Decrypt0r 2.0 is a highly effective ransomware variant that encrypts several file types, making them inaccessible to the user, and demands a payment of $300 U.S dollars in Bitcoin to decrypt the files.
Additional details on Wana Decrypt0r 2.0 and EternalBlue (MS17-010)
Wana Decrypt0r 2.0 is a variant of the WannaCrypt ransomware family that is currently being spread by exploiting EternalBlue (MS17-010). Wana Decrypt0r 2.0 encrypts several file types on an infected computer demands a ransom of $300 USD in Bitcoin to decrypt the inaccessible files.
ExternalBlue is an exploit that takes advantage of previous vulnerabilities in SMB, a critical protocol for Windows Systems. The exploit allows for the remote execution of malicious code on vulnerable systems without requiring any use interaction. The ExternalBlue exploit requires that the systems be vulnerable and expose the SMB service (enabled by default on Windows systems) to successfully compromise a system and replicate across network infrastructure to other vulnerable Windows systems.
At the time of this writing, this cyber-attack has quickly spread to 99 countries across multiple regions of the world. This global threat arrives in the form of a phishing email with a malicious attachment, once the malicious attachment is opened a dropper begins to download and unpack the actual ransomware code. The ransomware encrypts the user’s files, scans the networks to which the machine is connected, and uses the EternalBlue exploit to spread across organizations with unpatched Windows systems.
Kudelski Security has observed several industries and regions being specifically targeted by this ransomware campaign. Kudelski Security has intelligence that indicates that other ramsomware campaigns are actively integrating more of the Fuzzbunch framework exploits into their code.
As of this writing, according to internet scanning tool Shodan, there are approximately 2.4 million internet exposed systems which may be vulnerable to this exploit.
Mitigation and Response
Microsoft released a patch for the EternalBlue and other critical remote code execution vulnerabilities in March 2017 as part of Microsoft Security Bulletin MS17-010.
Kudelski Security recommends that clients immediately apply the patch for MS17-010. For organizations unable to quickly apply the Microsoft patches, potential mitigations include using a GPO to apply Windows Firewall rules to block inbound SMB connections on all unpatched endpoint systems and limiting SMB connections between servers.
Kudelski Security also recommends limiting all inbound and outbound communication on UDP ports 137 & 138 and TCP ports 139 & 445 on internet firewalls in order to reduce exposure and the slow the propagation of this ransomware.
Kudelski Security recommends backing up all files, including systems already affected by the ransomware in case future decryption tools become available.
Additionally, Kudelski Security recommends that organizations evaluate their vulnerability management programs to ensure that updates and patches are tested and applied quickly once they are released.
The Kudelski Security Cyber Fusion Center has ensured all managed and monitored security devices are updated with detection signatures and methodology to detect the uses of the Wana DeCrypt0r 2.0 ransomware and exploitation with ExternalBlue and other recent Windows exploits.
MS17-010 –Critical security advisory
VirusTotal analysis of malicious PDF:
Ransomware Dropper b9c5d4339809e0ad9a00d4d3dd26fdf44a32819a54abf846bb9b560d81391c25
184.108.40.206:9001 220.127.116.11:443 18.104.22.168:443 22.214.171.124:9001 126.96.36.199:443 188.8.131.52:443 184.108.40.206:9001 220.127.116.11:9004 18.104.22.168:443 22.214.171.124:9001 126.96.36.199:22
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