Sarina

I. Targeted Entities

U.S. Critical Infrastructures

II. Introduction

CISA, NSA, and FBI have confirmed that Volt Typhoon has compromised the IT environments of multiple critical infrastructure organizations—primarily in Communications, Energy, Transportation Systems, and Water and Wastewater Systems Sectors—in the continental and non-continental U.S. and its territories, including Guam.

Volt Typhoon’s choice of targets and pattern of behavior is not consistent with traditional cyber espionage or intelligence gathering operations, and the U.S. authoring agencies assess with high confidence that Volt Typhoon actors are pre-positioning themselves on IT networks to enable lateral movement to OT assets to disrupt functions.

These actors could use their network access for disruptive effects in the event of potential geopolitical tensions and/or military conflicts. (Cybersecurity and Infrastructure Security Agency, 2024)

III. Additional Background Information

In December 2023, an operation disrupted a botnet comprising hundreds of U.S.-based small office/home office (SOHO) routers that were hijacked by state-sponsored hackers from the People’s Republic of China (PRC). The hackers, known to the private sector as “Volt Typhoon,” used privately-owned SOHO routers infected with the “KV Botnet” malware to conceal the PRC origin of further hacking activities directed against the U.S. and other foreign victims. These further hacking activities included a campaign targeting critical infrastructure organizations in the U.S. and elsewhere that was the subject of a May 2023 FBI, National Security Agency, and CISA advisory (Office of Public Affairs, 2024).

The KV Botnet primarily targets Cisco and Net Gear routers, exploiting a vulnerability due to their “end of service” status. This means they were no longer receiving security patches or software updates from the manufacturer. The operation deleted the KV Botnet malware from the routers and took additional steps to sever their connection to the botnet, such as blocking communications with other devices used to control the botnet (Office of Public Affairs, 2024).

Volt Typhoon employs a multi-faceted approach to infiltrate and compromise target networks, starting with comprehensive pre-compromise reconnaissance to understand the network architecture and operational protocols. They exploit vulnerabilities in public-facing network appliances to gain initial access, then aim to escalate privileges within the network, often targeting administrator credentials. Utilizing valid credentials, they move laterally through the network, leveraging remote access services like Remote Desktop Protocol (RDP) to reach critical devices such as domain controllers (DC). Volt Typhoon conducts discovery within the network, utilizing stealthy tactics such as living-off-the-land (LOTL) binaries and PowerShell queries on event logs to extract critical information while minimizing detection. LOTL tools like ntdsutil, netsh, and systeminfo were used to gather information about the network service and system details. Also, Volt Typhoon implanted binary files such as SMSvcService.exe and Brightmetricagent.exe that can open reverse proxies between a compromised device and malicious C2 servers. The PowerShell script logins.ps1 was also observed collecting successful logon events on infected systems without being noticed. (Cybersecurity and Infrastructure Security Agency, 2024).

After achieving full domain compromise, Volt Typhoon extracts the Active Directory database (NTDS.dit) from the DC using techniques like the Volume Shadow Copy Service (VSS), bypassing file locking mechanisms. Additionally, Volt Typhoon uses offline password cracking methods to decipher hashed passwords, enabling elevated access within the network. With elevated credentials, Volt Typhoon focuses on strategic network infiltration, aiming to access Operational Technology (OT) assets, such as sensors and control systems. Volt Typhoon was observed testing access to OT systems using default vendor credentials and exploiting compromised credentials obtained through NTDS.dit theft. This access grants them the capability to potentially disrupt critical infrastructure systems such as HVAC and energy controls, indicating a significant threat to infrastructure security (Cybersecurity and Infrastructure Security Agency, 2024).

The second vulnerability, CVE-2024-1708, is related to CWE-22 – Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’). Although it is considered less severe as it is unlocked by CVE-2024-1079, it must not be underestimated (Team Huntress, 2024). This vulnerability involves manipulating ZIP file paths when extracting its contents. Attackers can then modify these contents and execute malicious code (Poudel, 2024). To do this, a malicious actor needs to have both administrative credentials and create a malicious extension inside C:Program Files (x86)ScreenConnectApp_Extensions to write files anywhere within the folder (Team Huntress, 2024). Team Huntress showed that this ZipSlip attack was not necessary, as malicious actors can run code by accessing a ScreenConnect feature called “Extensions”. This could potentially go easily unnoticed in a system since no other extensions need to be installed (Team Huntress, 2024).

ConnectWise released a patched version of ScreenConnect on February 21^st, 2024, and recommends updating all 23.9.7 and earlier versions to 23.9.8 (ConnectWise, 2024). As of today, February 22^nd, 2024, 3,800 instances of ScreenConnect have been found vulnerable, and need to be updated to the latest version in order to prevent malicious actors from accessing the ScreenConnect environment. ConnectWise added that Cloud instances were automatically patched, while On-Prem partners need to install all the required updates manually to remediate against both vulnerabilities (ConnectWise).

IV. MITRE ATT&CK

• T1592 – Gather Victim Host Information
  Adversaries may obtain crucial details about victim hosts, encompassing administrative data (e.g., name, assigned IP) and configuration specifics (e.g., operating system). This information is gathered through various methods, including direct actions like Active Scanning or Phishing, as well as compromising sites to collect data from visitors.

• T1583.003 – Acquire Infrastructure: Botnet
  Adversaries may obtain compromised systems through purchasing, leasing, or renting botnets, which are networks of compromised systems. By utilizing these botnets, adversaries can orchestrate coordinated tasks, including subscribing to services like booter/stresser to launch large-scale activities such as Phishing or Distributed Denial of Service (DDoS) attacks.

• T1190 – Exploit Public-Facing Application
  Adversaries may exploit weaknesses in internet-facing systems, targeting software bugs, glitches, or misconfigurations. This may involve websites, databases, standard services, or network protocols, potentially leading to compromise. Cloud-based or containerized applications could provide access to underlying infrastructure, cloud/container APIs, or exploitation of weak access management. Edge network infrastructure and appliances may also be targeted. Frameworks like OWASP and CWE can be used to identify common web vulnerabilities that adversaries may exploit.

• T1078 – Valid Accounts
  Adversaries leverage compromised credentials for various purposes such as Initial Access, Persistence, Privilege Escalation, or Defense Evasion. These credentials can circumvent access controls for resources, provide persistent access to remote systems, and access services like VPNs or Outlook Web Access. Adversaries often opt for legitimate access to evade detection, and inactive accounts may be exploited to avoid detection. The overlap of permissions across systems poses a risk, allowing adversaries to pivot and attain high-level access, bypassing enterprise controls.

• T1068 – Exploitation for Privilege Escalation
  Adversaries may exploit software vulnerabilities to elevate privileges, capitalizing on programming errors in operating systems or kernel code to execute adversary-controlled actions. When operating with lower privileges, adversaries target higher-privileged components to escalate access, potentially reaching SYSTEM or root permissions. By exploiting vulnerabilities in drivers, adversaries may introduce a Bring Your Own Vulnerable Driver (BYOVD) for kernel mode code execution.
• T1110.002 – Brute Force: Password Cracking
  Adversaries use password cracking techniques to recover usable credentials, especially plaintext passwords, when they obtain credential material like password hashes. Techniques like OS Credential Dumping and Data from Configuration Repository can provide hashed credentials. Adversaries may systematically guess passwords or use pre-computed rainbow tables outside the target network to crack hashes, obtaining plaintext passwords for unauthorized access.

• Other Relevant MITRE ATT&CK Techniques
  T1133, T1059, T1587.004, T1589, T1590, T1591, T1593.
  

VII. References

PRC State-Sponsored Actors Compromise and Maintain Persistent Access to U.S. Critical Infrastructure | Cybersecurity and Infrastructure Security Agency CISA. (2024, February 7). https://www.cisa.gov/news-events/cybersecurity-advisories/aa24038a#_Appendix_C:_MITRE

U.S. government disrupts botnet people’s republic of China used to conceal hacking of critical infrastructure. Office of Public Affairs | United States Department of Justice. (2024, January 31). https://www.justice.gov/opa/pr/us-government-disrupts-botnet-peoples-republic-china-used-conceal-hacking-critical

Threat Advisory created by The Cyber Florida Security Operations Center. Contributing Security Analysts: Alessandro Lovadina, Joy Boddu, Likhitha Duggi

I. Targeted Entities

ConnectWise ScreenConnect customers

II. Introduction

A critical authentication bypass has been discovered in ConnectWise’s ScreenConnect, a software for remote desktop access. This exploit potentially allows attackers access to confidential information and critical systems without needing the proper credentials. Once authenticated via the authentication bypass, attackers can leverage a path-traversal vulnerability to potentially execute remote code inside critical systems.

III. Additional Background Information

On February 19, 2024, ConnectWise released a Threat Advisory for patching multiple vulnerabilities discovered in the company’s ScreenConnect software. ScreenConnect is a remote desktop and access software that can be used for direct connections to desktops, mobile devices, and more. The vulnerabilities, CVE-2024-1709 and CVE-2024-1708, were first reported on February 13^th. These vulnerabilities have been classified as significantly exploitable with CVE-2024-1709 receiving a 10.0 critical base score and CVE-2024-1708 receiving an 8.4 high base score by NIST.

The first vulnerability, CVE-2024-1709, involves authentication bypass, which is directly related to CWE-288 – Authentication Bypass Using an Alternate Path or Channel. A flaw was found in a text file named “SetupWizard.aspx”, which has the functionality of setting up the administrative user and installing a license for the system. In unpatched versions, this setup file can be accessed even after the initial setup is completed. This is accomplished by adding additional components after the legitimate URL to SetupWizard.aspx (/SetupWizard.aspx/[anything]) and exploiting how the .NET framework handles URL paths. The code inside the text file does not check if the ScreenConnect instance setup has already been completed, making it possible for anyone to access the setup wizard and overwrite the internal user database, effectively gaining administrative access (Poudel, 2024).

The second vulnerability, CVE-2024-1708, is related to CWE-22 – Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’). Although it is considered less severe as it is unlocked by CVE-2024-1079, it must not be underestimated (Team Huntress, 2024). This vulnerability involves manipulating ZIP file paths when extracting its contents. Attackers can then modify these contents and execute malicious code (Poudel, 2024). To do this, a malicious actor needs to have both administrative credentials and create a malicious extension inside C:Program Files (x86)ScreenConnectApp_Extensions to write files anywhere within the folder (Team Huntress, 2024). Team Huntress showed that this ZipSlip attack was not necessary, as malicious actors can run code by accessing a ScreenConnect feature called “Extensions”. This could potentially go easily unnoticed in a system since no other extensions need to be installed (Team Huntress, 2024).

ConnectWise released a patched version of ScreenConnect on February 21^st, 2024, and recommends updating all 23.9.7 and earlier versions to 23.9.8 (ConnectWise, 2024). As of today, February 22^nd, 2024, 3,800 instances of ScreenConnect have been found vulnerable, and need to be updated to the latest version in order to prevent malicious actors from accessing the ScreenConnect environment. ConnectWise added that Cloud instances were automatically patched, while On-Prem partners need to install all the required updates manually to remediate against both vulnerabilities (ConnectWise).

V. MITRE ATT&CK

• T1190 – Exploit Public-Facing Applications
  Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network. The weakness in the system can be a software bug, a temporary glitch, or a misconfiguration. Adversaries exploited CVE-2023-3519 to implant a webshell on the organization’s NetScaler ADC appliance.

• T1068 – Exploitation for Privilege Escalation
  Adversaries may exploit software vulnerabilities to elevate privileges. Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code.

• T1105 – Ingress Tool Transfer
  Adversaries may transfer tools or other files from an external system into a compromised environment. Tools or files may be copied from an external adversary-controlled system to the victim network through the command-and-control channel or through alternate protocols such as ftp. Once present, adversaries may also transfer/spread tools between victim devices within a compromised environment.

• T1136 – Create Account
  Adversaries may create an account to maintain access to victim systems. With a sufficient level of access, creating such accounts may be used to establish secondary credentialed access that does not require persistent remote access tools to be deployed on the system.

• T1203 – Exploitation for Client Execution
  Adversaries may exploit software vulnerabilities in client applications to execute code. Vulnerabilities can exist in software due to insecure coding practices that can lead to unanticipated behavior. Adversaries can take advantage of certain vulnerabilities through targeted exploitation for the purpose of arbitrary code execution.

CVE-2024-1708

VII. Additional OSINT Information

Sigma rule for detecting requests made to the Setup Wizard with trailing paths (Huntress).

Sigma rule for detecting the ScreenConnect server writing to a temporary XML file (Huntress).

Setup Wizard YARA Rule for detecting Internet Information Services (IIS) log entries in reference to the SetupWizard (Huntress).

Sigma rule that alerts file modifications in the App_Extensions root directory (Huntress).

VIII. References

CVE-2024-1709. NIST. (n.d.-b). https://nvd.nist.gov/vuln/detail/CVE-2024-1709

CVE-2024-1708. NIST. (n.d.-a). https://nvd.nist.gov/vuln/detail/CVE-2024-1708

ConnectWise ScreenConnect 23.9.8 security fix. ConnectWise. (2024, February 19). https://www.connectwise.com/company/trust/security-bulletins/connectwise-screenconnect-23.9.8

Detection guidance for ConnectWise CWE-288. Huntress. (2024a, February 20). https://www.huntress.com/blog/detection-guidance-for-connectwise-cwe-288-2

Understanding the ConnectWise screenconnect CVE-2024-1709 & CVE-2024-1708: Huntress blog. Huntress. (2024, February 21). https://www.huntress.com/blog/a-catastrophe-for-control-understanding-the-screenconnect-authentication-bypass

Mitre ATT&CK®. MITRE. (n.d.). https://attack.mitre.org/

Poudel, S. (2024, February 22). Unveiling the ScreenConnect authentication bypass (CVE-2024-1709 & CVE-2024-1708). Logpoint. https://www.logpoint.com/en/blog/emerging-threats/screenconnect-authentication-bypass/

Threat Advisory created by The Cyber Florida Security Operations Center. Contributing Security Analysts: Alessandro Lovadina, Benjamin Price

I. Targeted Entities

• NetScaler Users*

II. Introduction

This cyberattack has been targeting NetScaler application delivery controller (ADC) and NetScaler Gateway; tools that improve the delivery speed of applications to an end user and provides secure remote access to application and services, respectively. Threat actors exploited this vulnerabiltiy as a zero-day attack to drop a webshell. The webshell allowed the threat actors access to the victim’s active directory (AD) and collect and exfiltrate data.

III. Additional Background Information

In June 2023, threat actors exploited a public facing applications called NetScaler Application Delivery Controller and NeScaler Gateway. Threat actors implanted a webshell on the organization’s NetScaler ADC appliance, and then abused elevation controls to initilalize an exploit chain to a binary file to extract data.

The affected versions following this vulnerability are for Netscaler and Netscaler Gateway: 13.1 before 13.1-40.13. Intially, CVE-2023-3519 was CVE-2019-19781 that as discovered in December 2019 and it attracted signifcant attention due to its potential to be exploited for the same purpose as it is being seen (unauthneticated remote code execution). In the 2019-29781 CVE attackers would gain access through Citrix NetScaler server to exploit public facing applications such as Citrix ADC and gateway and we can see that happening in the 2023-3519 CVE as well.

According to NISTs’ CVSS Severity and Metrics the vulnerability has been rate the following:

Threat Actor Activity
Victim 1

As part of their initial exploit chain [T1190], the threat actors uploaded a TGZ file [T1105] containing a generic webshell [T1505.003], discovery script [TA0007], and setuid binary [T1548.001] on the ADC appliance and conducted SMB scanning on the subnet [T1046].

Threat Actor Activity
Victim 2

Threat actors uploaded a PHP webshell *logouttm.php* [T1036.005], likely as part of their initial exploit chain, to */netscaler/ns_gui/vpn/. Within an hour of installing the webshell, the actors implanted an Executable and Linkable Format (ELF) binary pykeygen that set user unique identifier (UID) to root and executed /bin/sh [T1059.004] via setuid and execve syscall.* [T1106]. Note: A third party also observed threat actors use an ELF binary (named pip4) to execute /bin/sh via syscall and change the UID to root. pip4 was located at /var/python/bin.

With root level access, the actors used hands-on-keyboard for discovery. They queried the AD via ldapsearch for users, groups, and computers. They collected the data in gzipped text files renamed 1.css and 2.css and placed the files in /netscaler/ns_gui/vpn/ for exfiltration.

After exfiltrating the files, the actors deleted them from the system [T1070.004] as well as some access logs, error logs, and authentication logs [T1070.002]. The victim organization detected the intrusion and mitigated the activity but did not identify signs of additional malicious activity.

For command and control (C2), the actors appeared to use compromised pfSense devices [T1584]; the victim observed communications with two pfSense IP addresses indicating the actor was using them for multi-hop proxying C2 traffic [T1090.003].

Updated vulnerabilities affecting Netscaler ADC and Netscaler Gateway:

As of October 23^rd, Cyber Florida recived updates regarding vulnerabilities affecting Netscaler ADC and Netscaler Gateway. The vulnerabilities in mention: CVE-2023-4966 and CVE 2023-4967 both place high in the CVSS score for severity, and should be mitigated immediately. CVE-2023-4966, a sensitive information disclosure vulnerability, allows attackers to get access to large amounts of data in memory at the end of a buffer. Frequently seen within this attack vector are efforts to gain unauthetnicated access to previous session tokens that allow attackers impersonate authenticated users and their escalate priveleges. CVE 2023-4967, although less critical than the first observed vulnerability, is still a severe vulnerability that can lead to a Denial of Service (D.O.S) attack and cause great harm to a company.

As of October 23^rd, updated effected versions of Netscaler ADC and Netscaler Gateway are the following:

• Netscaler ADC and Netscaler Gateway 14.1 before 14.1-8.50
• Netscaler ADC and Netscaler Gateway 13.1 before 13.1-49.15
• Netscaler ADC and Netscaler Gateway 13.0 before 13.0-92.19

V. MITRE ATT&CK

• T1190 – Exploit Public-Facing Applications
  Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network. The weakness in the system can be a software bug, a temporary glitch, or a misconfiguration. Adversaries exploited CVE-2023-3519 to implant a webshell on the organization’s NetScaler ADC appliance.

• T1505.003 – Server Software Component: Web Shell
  Adversaries may backdoor web servers with web shells to establish persistent access to systems. The threat actors implanted a generic webshell on the organization’s NetScaler ADC appliance.

• T1548.001 – Abuse Elevation Control Mechanism: Setuid and Setgid
  An adversary may abuse configurations where an application has the setuid or setgid bits set in order to get code running in a different (and possibly more privileged) user’s context. As part of their initial exploit chain, the threat actors uploaded a TGZ file contain a setuid binary on the ADC appliance

• T1036.008 – Masquerading: Masquerade File Type
  Adversaries may masquerade malicious payloads as legitimate files through changes to the payload’s formatting, including the file’s signature, extension, and contents. Various file types have a typical standard format, including how they are encoded and organized. The threat actors exfiltrated data by uploading it as an image file to a web-accessible path.

• T1018 – Remote System Discovery
  Adversaries may attempt to get a listing of other systems by IP address, hostname, or other logical identifier on a network that may be used for Lateral Movement from the current system. Functionality could exist within remote access tools to enable this, but utilities available on the operating system could also be used such as Ping or net view using Net.The threat actors queried the AD for computers. The threat actors attempted to execute a subnet-wide curl command to identify what was accessible from within the network as well as potential lateral movement targets. Network-segmentation controls prevented this activity.

• T1016.001 – System Network Configuration Discovery: Internet Connection Discovery
  Adversaries may check for Internet connectivity on compromised systems. This may be performed during automated discovery and can be accomplished in numerous ways such as using Ping, tracert, and GET requests to websites.The threat actors attempted to verify outbound network connectivity with a ping command and executed host commands for a subnet-wide DNS lookup. Networksegmentation controls prevented this activity.

• T1046 – Network Service Discovery
  Adversaries may attempt to get a listing of services running on remote hosts and local network infrastructure devices, including those that may be vulnerable to remote software exploitation. Common methods to acquire this information include port and/or vulnerability scans using tools that are brought onto a system. The threat actors conducted SMB scanning on the organization’s subnet.

• T1056.001 – Archive Collected Data: Archive via Utility
  Adversaries may use utilities to compress and/or encrypt collected data prior to exfiltration. Many utilities include functionalities to compress, encrypt, or otherwise package data into a format that is easier/more secure to transport.The threat actors encrypted discovery data collected via openssl in “tar ball.”

• T1090.001 – Proxy: Internal Proxy
  Adversaries may use an internal proxy to direct command and control traffic between two or more systems in a compromised environment. Adversaries use internal proxies to manage command and control communications inside a compromised environment, to reduce the number of simultaneous outbound network connections, to provide resiliency in the face of connection loss, or to ride over existing trusted communications paths between infected systems to avoid suspicion.The actors likely used a PHP shell with proxying capability to attempt proxying SMB traffic to the DC (the traffic was blocked by a firewall and account restrictions).

• T1531 – Account Access Removal
  Adversaries may interrupt availability of system and network resources by inhibiting access to accounts utilized by legitimate users. Accounts may be deleted, locked, or manipulated (ex: changed credentials) to remove access to accounts. The threat actors deleted the authorization configuration file (/etc/auth.conf)—likely to prevent configured users from logging in remotely (e.g., CLI).

Cisa.gov

Third-party provide IP addresses afiliated with Citrix CVE-2023-3519

Cisa.gov

Third-party provided IOCs affiliated with Citrix CVE-2023-3519

Cisa.gov

Updated NetScaler ADC and NetScaler Gateway containing unathenticated buffer-related vulnerablities *10/23/2023*

Support.citrix.com

VIII. References

Threat actors exploiting Citrix CVE-2023-3519 to Implant Webshells – CISA. https://www.cisa.gov/sites/default/files/2023-07/aa23-201a_csa_threat_actors_exploiting_citrix-cve-2023-3519_to_implant_webshells.pdf

Enterprise Techniques. Mitre ATT&CK®. (n.d.). https://attack.mitre.org/versions/v13/techniques

NetScaler ADC and NetScaler Gateway Security Bulletin for CVE-2023-4966 and CVE-2023-4967. (2023, October 23). https://support.citrix.com/article/CTX579459/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20234966-and-cve20234967

Rapid. (n.d.). CVE-2023-4966: Exploitation of Citrix NetScaler Information Disclosure Vulnerability. Rapid7. https://www.rapid7.com/blog/post/2023/10/25/etr-cve-2023-4966-exploitation-of-citrix-netscaler-information-disclosure-vulnerability/#:~:text=On%20October%2010%2C%202023%2C%20Citrix,the%20end%20of%20a%20buffer.

Threat Advisory created by The Cyber Florida Security Operations Center. Contributing Security Analysts: EJ Bulut, Nahyan Jamil, Alessandro Lovadina, Ben Price, Erika Delvalle, Ariana Manrique, Yousef Blassy