This post was originally published on this site

Original release date: November 17, 2022

Summary

Actions to Take Today to Mitigate Cyber Threats from Ransomware:

• Prioritize remediating known exploited vulnerabilities.
• Enable and enforce multifactor authentication with strong passwords
• Close unused ports and remove any application not deemed necessary for day-to-day operations.

Note: This joint Cybersecurity Advisory (CSA) is part of an ongoing #StopRansomware effort to publish advisories for network defenders that detail various ransomware variants and ransomware threat actors. These #StopRansomware advisories include recently and historically observed tactics, techniques, and procedures (TTPs) and indicators of compromise (IOCs) to help organizations protect against ransomware. Visit stopransomware.gov to see all #StopRansomware advisories and to learn more about other ransomware threats and no-cost resources.

The Federal Bureau of Investigation (FBI), the Cybersecurity and Infrastructure Security Agency (CISA), and the Department of Health and Human Services (HHS) are releasing this joint CSA to disseminate known Hive IOCs and TTPs identified through FBI investigations as recently as November 2022.

FBI, CISA, and HHS encourage organizations to implement the recommendations in the Mitigations section of this CSA to reduce the likelihood and impact of ransomware incidents. Victims of ransomware operations should report the incident to their local FBI field office or CISA.

Download the PDF version of this report: pdf, 852.9 kb.

Technical Details

Note: This advisory uses the MITRE ATT&CK® for Enterprise framework, version 12. See MITRE ATT&CK for Enterprise for all referenced tactics and techniques.

As of November 2022, Hive ransomware actors have victimized over 1,300 companies worldwide, receiving approximately US$100 million in ransom payments, according to FBI information. Hive ransomware follows the ransomware-as-a-service (RaaS) model in which developers create, maintain, and update the malware, and affiliates conduct the ransomware attacks. From June 2021 through at least November 2022, threat actors have used Hive ransomware to target a wide range of businesses and critical infrastructure sectors, including Government Facilities, Communications, Critical Manufacturing, Information Technology, and especially Healthcare and Public Health (HPH).

The method of initial intrusion will depend on which affiliate targets the network. Hive actors have gained initial access to victim networks by using single factor logins via Remote Desktop Protocol (RDP), virtual private networks (VPNs), and other remote network connection protocols [T1133]. In some cases, Hive actors have bypassed multifactor authentication (MFA) and gained access to FortiOS servers by exploiting Common Vulnerabilities and Exposures (CVE) CVE-2020-12812. This vulnerability enables a malicious cyber actor to log in without a prompt for the user’s second authentication factor (FortiToken) when the actor changes the case of the username.

Hive actors have also gained initial access to victim networks by distributing phishing emails with malicious attachments [T1566.001] and by exploiting the following vulnerabilities against Microsoft Exchange servers [T1190]:

• CVE-2021-31207 – Microsoft Exchange Server Security Feature Bypass Vulnerability
• CVE-2021-34473 – Microsoft Exchange Server Remote Code Execution Vulnerability
• CVE-2021-34523 – Microsoft Exchange Server Privilege Escalation Vulnerability

After gaining access, Hive ransomware attempts to evade detention by executing processes to:

• Identify processes related to backups, antivirus/anti-spyware, and file copying and then terminating those processes to facilitate file encryption [T1562].
• Stop the volume shadow copy services and remove all existing shadow copies via vssadmin on command line or via PowerShell [T1059] [T1490].
• Delete Windows event logs, specifically the System, Security and Application logs [T1070].

Prior to encryption, Hive ransomware removes virus definitions and disables all portions of Windows Defender and other common antivirus programs in the system registry [T1112].

Hive actors exfiltrate data likely using a combination of Rclone and the cloud storage service Mega.nz [T1537]. In addition to its capabilities against the Microsoft Windows operating system, Hive ransomware has known variants for Linux, VMware ESXi, and FreeBSD.

During the encryption process, a file named *.key (previously *.key.*) is created in the root directory (C: or /root/). Required for decryption, this key file only exists on the machine where it was created and cannot be reproduced. The ransom note, HOW_TO_DECRYPT.txt is dropped into each affected directory and states the *.key file cannot be modified, renamed, or deleted, otherwise the encrypted files cannot be recovered [T1486]. The ransom note contains a “sales department” .onion link accessible through a TOR browser, enabling victim organizations to contact the actors through a live chat panel to discuss payment for their files. However, some victims reported receiving phone calls or emails from Hive actors directly to discuss payment.

The ransom note also threatens victims that a public disclosure or leak site accessible on the TOR site, “HiveLeaks”, contains data exfiltrated from victim organizations who do not pay the ransom demand (see figure 1 below). Additionally, Hive actors have used anonymous file sharing sites to disclose exfiltrated data (see table 1 below).

 

Table 1: Anonymous File Sharing Sites Used to Disclose Data

https://anonfiles[.]com

https://mega[.]nz

https://send.exploit[.]in

https://ufile[.]io

https://www.sendspace[.]com

https://privatlab[.]net

https://privatlab[.]com

 

Once the victim organization contacts Hive actors on the live chat panel, Hive actors communicate the ransom amount and the payment deadline. Hive actors negotiate ransom demands in U.S. dollars, with initial amounts ranging from several thousand to millions of dollars. Hive actors demand payment in Bitcoin.

Hive actors have been known to reinfect—with either Hive ransomware or another ransomware variant—the networks of victim organizations who have restored their network without making a ransom payment.

Indicators of Compromise

Threat actors have leveraged the following IOCs during Hive ransomware compromises. Note: Some of these indicators are legitimate applications that Hive threat actors used to aid in further malicious exploitation. FBI, CISA, and HHS recommend removing any application not deemed necessary for day-to-day operations. See tables 2–3 below for IOCs obtained from FBI threat response investigations as recently as November 2022.

Table 2: Known IOCs as of November 2022

Known IOCs – Files

HOW_TO_DECRYPT.txt typically in directories with encrypted files

*.key typically in the root directory, i.e., C: or /root

hive.bat

shadow.bat

asq.r77vh0[.]pw – Server hosted malicious HTA file

asq.d6shiiwz[.]pw – Server referenced in malicious regsvr32 execution

asq.swhw71un[.]pw – Server hosted malicious HTA file

asd.s7610rir[.]pw – Server hosted malicious HTA file

Windows_x64_encrypt.dll

Windows_x64_encrypt.exe

Windows_x32_encrypt.dll

Windows_x32_encrypt.exe

Linux_encrypt

Esxi_encrypt

Known IOCs – Events

System, Security and Application Windows event logs wiped

Microsoft Windows Defender AntiSpyware Protection disabled

Microsoft Windows Defender AntiVirus Protection disabled

Volume shadow copies deleted

Normal boot process prevented

Known IOCs – Logged Processes

wevtutil.exe cl system

wevtutil.exe cl security

wevtutil.exe cl application

vssadmin.exe delete shadows /all /quiet

wmic.exe SHADOWCOPY /nointeractive

wmic.exe shadowcopy delete

bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures

bcdedit.exe /set {default} recoveryenabled no

 

Table 3: Potential IOC IP Addresses as of November 2022

Note: Some of these observed IP addresses are more than a year old. FBI and CISA recommend vetting or investigating these IP addresses prior to taking forward-looking action like blocking.

Potential IOC IP Addresses for Compromise or Exfil:
84.32.188[.]57	84.32.188[.]238
93.115.26[.]251	185.8.105[.]67
181.231.81[.]239	185.8.105[.]112
186.111.136[.]37	192.53.123[.]202
158.69.36[.]149	46.166.161[.]123
108.62.118[.]190	46.166.161[.]93
185.247.71[.]106	46.166.162[.]125
5.61.37[.]207	46.166.162[.]96
185.8.105[.]103	46.166.169[.]34
5.199.162[.]220	93.115.25[.]139
5.199.162[.]229	93.115.27[.]148
89.147.109[.]208	83.97.20[.]81
5.61.37[.]207	5.199.162[.]220
5.199.162[.]229;	46.166.161[.]93
46.166.161[.]123;	46.166.162[.]96
46.166.162[.]125	46.166.169[.]34
83.97.20[.]81	84.32.188[.]238
84.32.188[.]57	89.147.109[.]208
93.115.25[.]139;	93.115.26[.]251
93.115.27[.]148	108.62.118[.]190
158.69.36[.]149/span>	181.231.81[.]239
185.8.105[.]67	185.8.105[.]103
185.8.105[.]112	185.247.71[.]106
186.111.136[.]37	192.53.123[.]202

 

MITRE ATT&CK TECHNIQUES

See table 4 for all referenced threat actor tactics and techniques listed in this advisory.

Table 4: Hive Actors ATT&CK Techniques for Enterprise

Initial Access
Technique Title	ID	Use
External Remote Services	T1133	Hive actors gain access to victim networks by using single factor logins via RDP, VPN, and other remote network connection protocols.
Exploit Public-Facing Application	T1190	Hive actors gain access to victim network by exploiting the following Microsoft Exchange vulnerabilities: CVE-2021-34473, CVE-2021-34523, CVE-2021-31207, CVE-2021-42321.
Phishing	T1566.001	Hive actors gain access to victim networks by distributing phishing emails with malicious attachments.
Execution
Technique Title	ID	Use
Command and Scripting Interpreter	T1059	Hive actors looks to stop the volume shadow copy services and remove all existing shadow copies via vssadmin on command line or PowerShell.
Defense Evasion
Technique Title	ID	Use
Indicator Removal on Host	T1070	Hive actors delete Windows event logs, specifically, the System, Security and Application logs.
Modify Registry	T1112	Hive actors set registry values for DisableAntiSpyware and DisableAntiVirus to 1.
Impair Defenses	T1562	Hive actors seek processes related to backups, antivirus/anti-spyware, and file copying and terminates those processes to facilitate file encryption.
Exfiltration
Technique Title	ID	Use
Transfer Data to Cloud Account	T1537	Hive actors exfiltrate data from victims, using a possible combination of Rclone and the cloud storage service Mega.nz.
Impact
Technique Title		Use
Data Encrypted for Impact	T1486	Hive actors deploy a ransom note HOW_TO_DECRYPT.txt into each affected directory which states the *.key file cannot be modified, renamed, or deleted, otherwise the encrypted files cannot be recovered.
Inhibit System Recovery	T1490	Hive actors looks to stop the volume shadow copy services and remove all existing shadow copies via vssadmin via command line or PowerShell.

Mitigations

FBI, CISA, and HHS recommend organizations, particularly in the HPH sector, implement the following to limit potential adversarial use of common system and network discovery techniques and to reduce the risk of compromise by Hive ransomware:

• Verify Hive actors no longer have access to the network.
• Install updates for operating systems, software, and firmware as soon as they are released. Prioritize patching VPN servers, remote access software, virtual machine software, and known exploited vulnerabilities. Consider leveraging a centralized patch management system to automate and expedite the process.
• Require phishing-resistant MFA for as many services as possible—particularly for webmail, VPNs, accounts that access critical systems, and privileged accounts that manage backups.
• If used, secure and monitor RDP.
  • Limit access to resources over internal networks, especially by restricting RDP and using virtual desktop infrastructure.
  • After assessing risks, if you deem RDP operationally necessary, restrict the originating sources and require MFA to mitigate credential theft and reuse.
  • If RDP must be available externally, use a VPN, virtual desktop infrastructure, or other means to authenticate and secure the connection before allowing RDP to connect to internal devices.
  • Monitor remote access/RDP logs, enforce account lockouts after a specified number of attempts to block brute force campaigns, log RDP login attempts, and disable unused remote access/RDP ports.
  • Be sure to properly configure devices and enable security features.
  • Disable ports and protocols not used for business purposes, such as RDP Port 3389/TCP.
• Maintain offline backups of data, and regularly maintain backup and restoration. By instituting this practice, the organization ensures they will not be severely interrupted, and/or only have irretrievable data.
• Ensure all backup data is encrypted, immutable (i.e., cannot be altered or deleted), and covers the entire organization’s data infrastructure. Ensure your backup data is not already infected.,
• Monitor cyber threat reporting regarding the publication of compromised VPN login credentials and change passwords/settings if applicable.
• Install and regularly update anti-virus or anti-malware software on all hosts.
• Enable PowerShell Logging including module logging, script block logging and transcription.
• Install an enhanced monitoring tool such as Sysmon from Microsoft for increased logging.
• Review the following additional resources.
  • The joint advisory from Australia, Canada, New Zealand, the United Kingdom, and the United States on Technical Approaches to Uncovering and Remediating Malicious Activity provides additional guidance when hunting or investigating a network and common mistakes to avoid in incident handling.
  • The Cybersecurity and Infrastructure Security Agency-Multi-State Information Sharing & Analysis Center Joint Ransomware Guide covers additional best practices and ways to prevent, protect, and respond to a ransomware attack.
  • StopRansomware.gov is the U.S. Government’s official one-stop location for resources to tackle ransomware more effectively.

If your organization is impacted by a ransomware incident, FBI, CISA, and HHS recommend the following actions.

• Isolate the infected system. Remove the infected system from all networks, and disable the computer’s wireless, Bluetooth, and any other potential networking capabilities. Ensure all shared and networked drives are disconnected.
• Turn off other computers and devices. Power-off and segregate (i.e., remove from the network) the infected computer(s). Power-off and segregate any other computers or devices that share a network with the infected computer(s) that have not been fully encrypted by ransomware. If possible, collect and secure all infected and potentially infected computers and devices in a central location, making sure to clearly label any computers that have been encrypted. Powering-off and segregating infected computers and computers that have not been fully encrypted may allow for the recovery of partially encrypted files by specialists.
• Secure your backups. Ensure that your backup data is offline and secure. If possible, scan your backup data with an antivirus program to check that it is free of malware.

In addition, FBI, CISA, and HHS urge all organizations to apply the following recommendations to prepare for, mitigate/prevent, and respond to ransomware incidents.

Preparing for Cyber Incidents

• Review the security posture of third-party vendors and those interconnected with your organization. Ensure all connections between third-party vendors and outside software or hardware are monitored and reviewed for suspicious activity.
• Implement listing policies for applications and remote access that only allow systems to execute known and permitted programs under an established security policy.
• Document and monitor external remote connections. Organizations should document approved solutions for remote management and maintenance, and immediately investigate if an unapproved solution is installed on a workstation.
• Implement a recovery plan to maintain and retain multiple copies of sensitive or proprietary data and servers in a physically separate, segmented, and secure location (i.e., hard drive, storage device, the cloud).

Identity and Access Management

• Require all accounts with password logins (e.g., service account, admin accounts, and domain admin accounts) to comply with National Institute of Standards and Technology (NIST) standards for developing and managing password policies.
  • Use longer passwords consisting of at least 8 characters and no more than 64 characters in length.
  • Store passwords in hashed format using industry-recognized password managers.
  • Add password user “salts” to shared login credentials.
  • Avoid reusing passwords.
  • Implement multiple failed login attempt account lockouts.
  • Disable password “hints.”
  • Refrain from requiring password changes more frequently than once per year unless a password is known or suspected to be compromised.
    Note: NIST guidance suggests favoring longer passwords instead of requiring regular and frequent password resets. Frequent password resets are more likely to result in users developing password “patterns” cyber criminals can easily decipher.
  • Require administrator credentials to install software.
• Require phishing-resistant multifactor authentication for all services to the extent possible, particularly for webmail, virtual private networks, and accounts that access critical systems.
• Review domain controllers, servers, workstations, and active directories for new and/or unrecognized accounts.
• Audit user accounts with administrative privileges and configure access controls according to the principle of least privilege.
• Implement time-based access for accounts set at the admin level and higher. For example, the Just-in-Time (JIT) access method provisions privileged access when needed and can support enforcement of the principle of least privilege (as well as the Zero Trust model). This is a process where a network-wide policy is set in place to automatically disable admin accounts at the Active Directory level when the account is not in direct need. Individual users may submit their requests through an automated process that grants them access to a specified system for a set timeframe when they need to support the completion of a certain task. 

Protective Controls and Architecture

• Segment networks to prevent the spread of ransomware. Network segmentation can help prevent the spread of ransomware by controlling traffic flows between—and access to—various subnetworks and by restricting adversary lateral movement.
• Identify, detect, and investigate abnormal activity and potential traversal of the indicated ransomware with a networking monitoring tool. To aid in detecting the ransomware, implement a tool that logs and reports all network traffic, including lateral movement activity on a network. Endpoint detection and response (EDR) tools are particularly useful for detecting lateral connections as they have insight into common and uncommon network connections for each host.
• Install, regularly update, and enable real time detection for antivirus software on all hosts.

Vulnerability and Configuration Management

• Consider adding an email banner to emails received from outside your organization.
• Disable command-line and scripting activities and permissions. Privilege escalation and lateral movement often depend on software utilities running from the command line. If threat actors are not able to run these tools, they will have difficulty escalating privileges and/or moving laterally.
• Ensure devices are properly configured and that security features are enabled. 
• Restrict Server Message Block (SMB) Protocol within the network to only access necessary servers and remove or disable outdated versions of SMB (i.e., SMB version 1). Threat actors use SMB to propagate malware across organizations.

REFERENCES

• Stopransomware.gov is a whole-of-government approach that gives one central location for ransomware resources and alerts.
• Resource to mitigate a ransomware attack: CISA-Multi-State Information Sharing and Analysis Center (MS-ISAC) Joint Ransomware Guide.
• No-cost cyber hygiene services: Cyber Hygiene Services and Ransomware Readiness Assessment.

INFORMATION REQUESTED

The FBI, CISA, and HHS do not encourage paying a ransom to criminal actors. Paying a ransom may embolden adversaries to target additional organizations, encourage other criminal actors to engage in the distribution of ransomware, and/or fund illicit activities. Paying the ransom also does not guarantee that a victim’s files will be recovered. However, the FBI, CISA, and HHS understand that when businesses are faced with an inability to function, executives will evaluate all options to protect their shareholders, employees, and customers. Regardless of whether you or your organization decide to pay the ransom, the FBI, CISA, and HHS urge you to promptly report ransomware incidents to your local FBI field office, or to CISA at report@cisa.gov or (888) 282-0870. Doing so provides investigators with the critical information they need to track ransomware attackers, hold them accountable under US law, and prevent future attacks. 

The FBI may seek the following information that you determine you can legally share, including:

• Recovered executable files
• Live random access memory (RAM) capture
• Images of infected systems
• Malware samples
• IP addresses identified as malicious or suspicious
• Email addresses of the attackers
• A copy of the ransom note
• Ransom amount
• Bitcoin wallets used by the attackers
• Bitcoin wallets used to pay the ransom
• Post-incident forensic reports

DISCLAIMER

The information in this report is being provided “as is” for informational purposes only. FBI, CISA, and HHS do not endorse any commercial product or service, including any subjects of analysis. Any reference to specific commercial products, processes, or services by service mark, trademark, manufacturer, or otherwise, does not constitute or imply endorsement, recommendation, or favoring by FBI, CISA, or HHS.

 

Revisions

• Initial Version: November 17, 2022

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This post was originally published on this site

Original release date: November 16, 2022

Summary

From mid-June through mid-July 2022, CISA conducted an incident response engagement at a Federal Civilian Executive Branch (FCEB) organization where CISA observed suspected advanced persistent threat (APT) activity. In the course of incident response activities, CISA determined that cyber threat actors exploited the Log4Shell vulnerability in an unpatched VMware Horizon server, installed XMRig crypto mining software, moved laterally to the domain controller (DC), compromised credentials, and then implanted Ngrok reverse proxies on several hosts to maintain persistence. CISA and the Federal Bureau of Investigation (FBI) assess that the FCEB network was compromised by Iranian government-sponsored APT actors.

CISA and FBI are releasing this Cybersecurity Advisory (CSA) providing the suspected Iranian government-sponsored actors’ tactics, techniques, and procedures (TTPs) and indicators of compromise (IOCs) to help network defenders detect and protect against related compromises.

CISA and FBI encourage all organizations with affected VMware systems that did not immediately apply available patches or workarounds to assume compromise and initiate threat hunting activities. If suspected initial access or compromise is detected based on IOCs or TTPs described in this CSA, CISA and FBI encourage organizations to assume lateral movement by threat actors, investigate connected systems (including the DC), and audit privileged accounts. All organizations, regardless of identified evidence of compromise, should apply the recommendations in the Mitigations section of this CSA to protect against similar malicious cyber activity.

For more information on Iranian government-sponsored Iranian malicious cyber activity, see CISA’s Iran Cyber Threat Overview and Advisories webpage and FBI’s Iran Threats webpage.

Download the PDF version of this report: pdf, 528 kb.

For a downloadable copy of the Malware Analysis Report (MAR) accompanying this report, see: MAR 10387061-1.v1.

Technical Details

Note: This advisory uses the MITRE ATT&CK for Enterprise framework, version 11. See the MITRE ATT&CK Tactics and Techniques section for a table of the threat actors’ activity mapped to MITRE ATT&CK® tactics and techniques with corresponding mitigation and/or detection recommendations.

Overview

In April 2022, CISA conducted retrospective analysis using EINSTEIN—an FCEB-wide intrusion detection system (IDS) operated and monitored by CISA—and identified suspected APT activity on an FCEB organization’s network. CISA observed bi-directional traffic between the network and a known malicious IP address associated with exploitation of the Log4Shell vulnerability (CVE-2021-44228) in VMware Horizon servers. In coordination with the FCEB organization, CISA initiated threat hunting incident response activities; however, prior to deploying an incident response team, CISA observed additional suspected APT activity. Specifically, CISA observed HTTPS activity from IP address 51.89.181[.]64 to the organization’s VMware server. Based on trusted third-party reporting, 51.89.181[.]64 is a Lightweight Directory Access Protocol (LDAP) server associated with threat actors exploiting Log4Shell. Following HTTPS activity, CISA observed a suspected LDAP callback on port 443 to this IP address. CISA also observed a DNS query for us‐nation‐ny[.]cf that resolved back to 51.89.181[.]64 when the victim server was returning this Log4Shell LDAP callback to the actors’ server.

CISA assessed that this traffic indicated a confirmed compromise based on the successful callback to the indicator and informed the organization of these findings; the organization investigated the activity and found signs of compromise. As trusted-third party reporting associated Log4Shell activity from 51.89.181[.]64 with lateral movement and targeting of DCs, CISA suspected the threat actors had moved laterally and compromised the organization’s DC.

From mid-June through mid-July 2022, CISA conducted an onsite incident response engagement and determined that the organization was compromised as early as February 2022, by likely Iranian government-sponsored APT actors who installed XMRig crypto mining software. The threat actors also moved laterally to the domain controller, compromised credentials, and implanted Ngrok reverse proxies.

Threat Actor Activity

In February 2022, the threat actors exploited Log4Shell [T1190] for initial access [TA0001] to the organization’s unpatched VMware Horizon server. As part of their initial exploitation, CISA observed a connection to known malicious IP address 182.54.217[.]2 lasting 17.6 seconds.

The actors’ exploit payload ran the following PowerShell command [T1059.001] that added an exclusion tool to Windows Defender [T1562.001]:

powershell try{Add-MpPreference -ExclusionPath ‘C:’; Write-Host ‘added-exclusion’} catch {Write-Host ‘adding-exclusion-failed’ }; powershell -enc “$BASE64 encoded payload to download next stage and execute it”

The exclusion tool allowlisted the entire c:drive, enabling threat actors to download tools to the c:drive without virus scans. The exploit payload then downloaded mdeploy.text from 182.54.217[.]2/mdepoy.txt to C:userspublicmde.ps1 [T1105]. When executed, mde.ps1 downloaded file.zip from 182.54.217[.]2 and removed mde.ps1 from the disk [T1070.004].

file.zip contained XMRig cryptocurrency mining software and associated configuration files.

• WinRing0x64.sys – XMRig Miner driver
• wuacltservice.exe – XMRig Miner
• config.json – XMRig miner configuration
• RuntimeBroker.exe – Associated file. This file can create a local user account [T1136.001] and tests for internet connectivity by pinging 8.8.8.8 [T1016.001]. The exploit payload created a Scheduled Task [T1053.005] that executed RuntimeBroker.exe daily as SYSTEM. Note: By exploiting Log4Shell, the actors gained access to a VMware service account with administrator and system level access. The Scheduled Task was named RuntimeBrokerService.exe to masquerade as a legitimate Windows task.

See MAR 10387061-1.v1 for additional information, including IOCs, on these four files.

After obtaining initial access and installing XMRig on the VMWare Horizon server, the actors used RDP [T1021.001] and the built-in Windows user account DefaultAccount [T1078.001] to move laterally [TA0008] to a VMware VDI-KMS host. Once the threat actor established themselves on the VDI-KMS host, CISA observed the actors download around 30 megabytes of files from transfer[.]sh server associated with 144.76.136[.]153. The actors downloaded the following tools:

• PsExec – a Microsoft signed tool for system administrators.
• Mimikatz – a credential theft tool.
• Ngrok – a reverse proxy tool for proxying an internal service out onto an Ngrok domain, which the user can then access at a randomly generated subdomain at *.ngrok[.]io. CISA has observed this tool in use by some commercial products for benign purposes; however, this process bypasses typical firewall controls and may be a potentially unwanted application in production environments. Ngrok is known to be used for malicious purposes.[1]

The threat actors then executed Mimikatz on VDI-KMS to harvest credentials and created a rogue domain administrator account [T1136.002]. Using the newly created account, the actors leveraged RDP to propagate to several hosts within the network. Upon logging into each host, the actors manually disabled Windows Defender via the Graphical User Interface (GUI) and implanted Ngrok executables and configuration files. The threat actors were able to implant Ngrok on multiple hosts to ensure Ngrok’s persistence should they lose access to a machine during a routine reboot. The actors were able to proxy [T1090] RDP sessions, which were only observable on the local network as outgoing HTTPS port 443 connections to tunnel.us.ngrok[.]com and korgn.su.lennut[.]com (the prior domain in reverse). It is possible, but was not observed, that the threat actors configured a custom domain, or used other Ngrok tunnel domains, wildcarded here as *.ngrok[.]com, *.ngrok[.]io, ngrok.*.tunnel[.]com, or korgn.*.lennut[.]com.

Once the threat actors established a deep foothold in the network and moved laterally to the domain controller, they executed the following PowerShell command on the Active Directory to obtain a list of all machines attached to the domain [T1018]:

Powershell.exe get-adcomputer -filter * -properties * | select name,operatingsystem,ipv4address >

The threat actors also changed the password for the local administrator account [T1098] on several hosts as a backup should the rogue domain administrator account get detected and terminated. Additionally, the threat actor was observed attempting to dump the Local Security Authority Subsystem Service (LSASS) process [T1003.001] with task manager but this was stopped by additional anti-virus the FCEB organization had installed.

MITRE ATT&CK TACTICS AND TECHNIQUES

See table 1 for all referenced threat actor tactics and techniques in this advisory, as well as corresponding detection and/or mitigation recommendations. For additional mitigations, see the Mitigations section.

Table 1: Cyber Threat Actors ATT&CK Techniques for Enterprise

Initial Access
Technique Title	ID	Use	Recommendations
Exploit Public-Facing Application	T1190	The actors exploited Log4Shell for initial access to the organization’s VMware Horizon server.	Mitigation/Detection: Use a firewall or web-application firewall and enable logging to prevent and detect potential Log4Shell exploitation attempts [M1050]. Mitigation: Perform regular vulnerability scanning to detect Log4J vulnerabilities and update Log4J software using vendor provided patches [M1016],[M1051].
Execution
Technique Title	ID	Use	Recommendation
Command and Scripting Interpreter: PowerShell	T1059.001	The actors ran PowerShell commands that added an exclusion tool to Windows Defender. The actors executed PowerShell on the AD to obtain a list of machines on the domain.	Mitigation: Disable or remove PowerShell for non-administrative users [M1042],[M1026] or enable code-signing to execute only signed scripts [M1045]. Mitigation: Employ anti-malware to automatically detect and quarantine malicious scripts [M1049].
Persistence
Technique Title	ID	Use	Recommendations
Account Manipulation	T1098	The actors changed the password for the local administrator account on several hosts.	Mitigation: Use multifactor authentication for user and privileged accounts [M1032]. Detection: Monitor events for changes to account objects and/or permissions on systems and the domain, such as event IDs 4738, 4728, and 4670. Monitor for modification of accounts in correlation with other suspicious activity [DS0002].
Create Account: Local Account	T1136.001	The actors’ malware can create local user accounts.	Mitigation: Configure access controls and firewalls to limit access to domain controllers and systems used to create and manage accounts. Detection: Monitor executed commands and arguments for actions that are associated with local account creation, such as net user /add , useradd, and dscl -create [DS0017]. Detection: Enable logging for new user creation [DS0002].
Create Account: Domain Account	T1136.002	The actors used Mimikatz to create a rogue domain administrator account.	Mitigation: Configure access controls and firewalls to limit access to domain controllers and systems used to create and manage accounts. Detection: Enable logging for new user creation, especially domain administrator accounts [DS0002].
Scheduled Task/Job: Scheduled Task	T1053.005	The actors’ exploit payload created Scheduled Task RuntimeBrokerService.exe, which executed RuntimeBroker.exe daily as SYSTEM.	Mitigation: Configure settings for scheduled tasks to force tasks to run under the context of the authenticated account instead of allowing them to run as SYSTEM [M1028]. Detection: Monitor for newly constructed processes and/or command-lines that execute from the svchost.exe in Windows 10 and the Windows Task Scheduler taskeng.exe for older versions of Windows [DS0009] Detection: Monitor for newly constructed scheduled jobs by enabling the Microsoft-Windows-TaskScheduler/Operational setting within the event logging service [DS0003].
Valid Accounts: Default Accounts	T1078.001	The actors used built-in Windows user account DefaultAccount.	Mitigation: Change default usernames and passwords immediately after the installation and before deployment to a production environment [M1027]. Detection: Develop rules to monitor logon behavior across default accounts that have been activated or logged into [DS0028].
Defense Evasion
Technique Title	ID	Use	Recommendations
Impair Defenses: Disable or Modify Tools	T1562.001	The actors added an exclusion tool to Windows Defender. The tool allowlisted the entire c:drive, enabling the actors to bypass virus scans for tools they downloaded to the c:drive. The actors manually disabled Windows Defender via the GUI.	Mitigation: Ensure proper user permissions are in place to prevent adversaries from disabling or interfering with security services. [M1018]. Detection: Monitor for changes made to Windows Registry keys and/or values related to services and startup programs that correspond to security tools such as HKLM:SOFTWAREPoliciesMicrosoftWindows Defender [DS0024]. Detection: Monitor for telemetry that provides context for modification or deletion of information related to security software processes or services such as Windows Defender definition files in Windows and System log files in Linux [DS0013]. Detection: Monitor processes for unexpected termination related to security tools/services [DS0009].
Indicator Removal on Host: File Deletion	T1070.004	The actors removed malicious file mde.ps1 from the dis.	Detection: Monitor executed commands and arguments for actions that could be utilized to unlink, rename, or delete files [DS0017]. Detection: Monitor for unexpected deletion of files from the system [DS0022].
Credential Access
Technique Title	ID	Use	Recommendations
OS Credential Dumping: LSASS Memory	T1003.001	The actors were observed trying to dump LSASS process.	Mitigation: With Windows 10, Microsoft implemented new protections called Credential Guard to protect the LSA secrets that can be used to obtain credentials through forms of credential dumping [M1043] Mitigation: On Windows 10, enable Attack Surface Reduction (ASR) rules to secure LSASS and prevent credential stealing [M1040]. Mitigation: Ensure that local administrator accounts have complex, unique passwords across all systems on the network [M1027]. Detection: Monitor for unexpected processes interacting with LSASS.exe. Common credential dumpers such as Mimikatz access LSASS.exe by opening the process, locating the LSA secrets key, and decrypting the sections in memory where credential details are stored. [DS0009]. Detection: Monitor executed commands and arguments that may attempt to access credential material stored in the process memory of the LSASS [DS0017].
Credentials from Password Stores	T1555	The actors used Mimikatz to harvest credentials.	Mitigation: Organizations may consider weighing the risk of storing credentials in password stores and web browsers. If system, software, or web browser credential disclosure is a significant concern, technical controls, policy, and user training may be used to prevent storage of credentials in improper locations [M1027]. Detection: Monitor for processes being accessed that may search for common password storage locations to obtain user credentials [DS0009]. Detection: Monitor executed commands and arguments that may search for common password storage locations to obtain user credentials [DS0017].
Discovery
Technique Title	ID	Use	Recommendations
Remote System Discovery	T1018	The actors executed a PowerShell command on the AD to obtain a list of all machines attached to the domain.	Detection: Monitor executed commands and arguments that 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 [DS0017]. Detection: Monitor for newly constructed network connections associated with pings/scans that 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 [DS0029]. Detection: Monitor for newly executed processes that can be used to discover remote systems, such as ping.exe and tracert.exe, especially when executed in quick succession [DS0009].
System Network Configuration Discovery: Internet Connection Discovery	T1016.001	The actors’ malware tests for internet connectivity by pinging 8.8.8.8.	Mitigation: Monitor executed commands, arguments [DS0017] and executed processes (e.g., tracert or ping) [DS0009] that may check for internet connectivity on compromised systems.
Lateral Movement
Technique Title	ID	Use	Recommendations
Remote Services: Remote Desktop Protocol	T1021.001	The actors used RDP to move laterally to multiple hosts on the network.	Mitigation: Use MFA for remote logins [M1032]. Mitigation: Disable the RDP service if it is unnecessary [M1042]. Mitigation: Do not leave RDP accessible from the internet. Enable firewall rules to block RDP traffic between network security zones within a network [M1030]. Mitigation: Consider removing the local Administrators group from the list of groups allowed to log in through RDP [M1026]. Detection: Monitor for user accounts logged into systems associated with RDP (ex: Windows EID 4624 Logon Type 10). Other factors, such as access patterns (ex: multiple systems over a relatively short period of time) and activity that occurs after a remote login, may indicate suspicious or malicious behavior with RDP [DS0028].
Command and Control
Technique Title	ID	Use	Recommendations
Proxy	T1090	The actors used Ngrok to proxy RDP connections and to perform command and control.	Mitigation: Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network allow and block lists [M1037]. Detection: Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g., extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure) [DS0029].
Ingress Tool Transfer	T1105	The actors downloaded malware and multiple tools to the network, including PsExec, Mimikatz, and Ngrok.	Mitigation: Employ anti-malware to automatically detect and quarantine malicious scripts [M1049].

 

INCIDENT RESPONSE

If suspected initial access or compromise is detected based on IOCs or TTPs in this CSA, CISA encourages organizations to assume lateral movement by threat actors and investigate connected systems and the DC.

CISA recommends organizations apply the following steps before applying any mitigations, including patching.

1. Immediately isolate affected systems.
2. Collect and review relevant logs, data, and artifacts. Take a memory capture of the device(s) and a forensic image capture for detailed analysis.
3. Consider soliciting support from a third-party incident response organization that can provide subject matter expertise to ensure the actor is eradicated from the network and to avoid residual issues that could enable follow-on exploitation.
4. Report incidents to CISA via CISA’s 24/7 Operations Center (report@cisa.gov or 888-282-0870) or your local FBI field office, or FBI’s 24/7 Cyber Watch (CyWatch) at (855) 292-3937 or by e-mail at CyWatch@fbi.gov.
    

Mitigations

CISA and FBI recommend implementing the mitigations below and in Table 1 to improve your organization’s cybersecurity posture on the basis of threat actor behaviors.

• Install updated builds to ensure affected VMware Horizon and UAG systems are updated to the latest version.
  • If updates or workarounds were not promptly applied following VMware’s release of updates for Log4Shell in December 2021, treat those VMware Horizon systems as compromised. Follow the pro-active incident response procedures outlined above prior to applying updates. If no compromise is detected, apply these updates as soon as possible.
    • See VMware Security Advisory VMSA-2021-0028.13 and VMware Knowledge Base (KB) 87073 to determine which VMware Horizon components are vulnerable.
    • Note: Until the update is fully implemented, consider removing vulnerable components from the internet to limit the scope of traffic. While installing the updates, ensure network perimeter access controls are as restrictive as possible.
    • If upgrading is not immediately feasible, see KB87073 and KB87092 for vendor-provided temporary workarounds. Implement temporary solutions using an account with administrative privileges. Note that these temporary solutions should not be treated as permanent fixes; vulnerable components should be upgraded to the latest build as soon as possible.
    • Prior to implementing any temporary solution, ensure appropriate backups have been completed.
    • Verify successful implementation of mitigations by executing the vendor supplied script Horizon_Windows_Log4j_Mitigations.zip without parameters to ensure that no vulnerabilities remain. See KB87073 for details.
• Keep all software up to date and prioritize patching known exploited vulnerabilities (KEVs).
• Minimize the internet-facing attack surface by hosting essential services on a segregated DMZ, ensuring strict network perimeter access controls, and not hosting internet-facing services that are not essential to business operations. Where possible, implement regularly updated web application firewalls (WAF) in front of public-facing services. WAFs can protect against web-based exploitation using signatures and heuristics that are likely to block or alert on malicious traffic.
• Use best practices for identity and access management (IAM) by implementing phishing resistant multifactor authentication (MFA), enforcing use of strong passwords, regularly auditing administrator accounts and permissions, and limiting user access through the principle of least privilege. Disable inactive accounts uniformly across the AD, MFA systems, etc.
  • If using Windows 10 version 1607 or Windows Server 2016 or later, monitor or disable Windows DefaultAccount, also known as the Default System Managed Account (DSMA).
• Audit domain controllers to log successful Kerberos Ticket Granting Service (TGS) requests and ensure the events are monitored for anomalous activity.  
  • Secure accounts.
  • Enforce the principle of least privilege. Administrator accounts should have the minimum permission necessary to complete their tasks.
  • Ensure there are unique and distinct administrative accounts for each set of administrative tasks.
  • Create non-privileged accounts for privileged users and ensure they use the non-privileged accounts for all non-privileged access (e.g., web browsing, email access).
• Create a deny list of known compromised credentials and prevent users from using known-compromised passwords.
• Secure credentials by restricting where accounts and credentials can be used and by using local device credential protection features. 
  • Use virtualizing solutions on modern hardware and software to ensure credentials are securely stored.
  • Ensure storage of clear text passwords in LSASS memory is disabled. Note: For Windows 8, this is enabled by default. For more information see Microsoft Security Advisory Update to Improve Credentials Protection and Management.
  • Consider disabling or limiting NTLM and WDigest Authentication.
  • Implement Credential Guard for Windows 10 and Server 2016 (refer to Microsoft: Manage Windows Defender Credential Guard for more information). For Windows Server 2012R2, enable Protected Process Light for Local Security Authority (LSA).
  • Minimize the AD attack surface to reduce malicious ticket-granting activity. Malicious activity such as “Kerberoasting” takes advantage of Kerberos’ TGS and can be used to obtain hashed credentials that threat actors attempt to crack.
     

VALIDATE SECURITY CONTROLS

In addition to applying mitigations, CISA and FBI recommend exercising, testing, and validating your organization’s security program against the threat behaviors mapped to the MITRE ATT&CK for Enterprise framework in this advisory. CISA and FBI recommend testing your existing security controls inventory to assess how they perform against the ATT&CK techniques described in this advisory.

To get started:

1. Select an ATT&CK technique described in this advisory (see table 1).
2. Align your security technologies against the technique.
3. Test your technologies against the technique.
4. Analyze your detection and prevention technologies performance.
5. Repeat the process for all security technologies to obtain a set of comprehensive performance data.
6. Tune your security program, including people, processes, and technologies, based on the data generated by this process.

CISA and FBI recommend continually testing your security program, at scale, in a production environment to ensure optimal performance against the MITRE ATT&CK techniques identified in this advisory.

References

• [1] MITRE ATT&CK Version 11: Software – Ngrok

Revisions

• Initial Version: November 16, 2022

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