Trend Micro Inc.

09/24/2021 | News release | Distributed by Public on 09/24/2021 08:42

Examining the Cring Ransomware Techniques

The Cringransomwaremade headlines as the threat was used in an attack thatexploited a bugin the 11-year-old version of the Adobe ColdFusion 9 software.

This has been the first recorded incident involving Cring operators' use of the said vulnerability. Past Cring attacks either abused unsecure remote desktop protocol (RDP) or virtual private network (VPN)vulnerabilitiesto gain initial access.

Ransom.Win32.CRING.Cis our detection name for the executable, whileRansom.MSIL.CRYNG.Ais the detection name that is used to detect C#-based samples for the same ransomware.

In this entry, we look at the techniques typically employed by this ransomware, as well as the most affected regions and industries.

The Cring ransomware techniques

Figure 1. The Cring ransomware infection chain

Here is a more detailed description of this chain:

Initial Access

The Cring ransomware gains initial access either through unsecure or compromised RDP or valid accounts.

The ransomware can also get into the system through certain vulnerability exploits.. The abuse of the aforementioned Adobe ColdFusion flaw (CVE-2010-2861) to enter the system is a new development for the threat. In the past, Cring was also used to exploit a FortiGate VPN server vulnerability (CVE-2018-13379).

Credential Access

Threat actors behind Cring usedweaponized toolsin their attacks. One of these tools is Mimikatz, which was used to steal account credentials of users who had previously logged into the system.

Lateral Movement and Defense Evasion

Lateral movement was done through Cobalt Strike. This tool was also used to distribute BAT files that will be used later for various purposes, including impairing the system's defenses.

Command and Control and Execution

Cobalt Strike was also used to continuously communicate with the maincommand-and-control(C&C) server.

BAT files were used to download and execute the Cring ransomware on the other systems in the compromised network. It also uses the Windows CertUtil program to help with the said download.

Impact

Once Cringhas been executed in the system, it disables services and processes that might hinder the ransomware's encryption routine. The threat will also delete backup files and folders. This will make restoring the encrypted files difficult for the victim, thereby placing more pressure on them to pay the ransom.

The ransomware will then proceed with its encryption routine and delete itself using a BAT file.

Regions and industries with the Cring ransomware detections

Based on our data, most of the Cring ransomware detections for attempted attacks were observed in Europe and the Middle East and Africa (EMEA) region. There have also been incidents in the Latin American Region (LAR), Asia Pacific (APAC), and North America (NABU).

The affected countries in the said regions were Azerbaijan, Brazil, Italy, Mexico, Saudi Arabia, the United States, and Turkey. With regard to industries, detections affected the finance and transportation sectors. Indeed, ransomware has been consistently attacking critical industries, as we discuss ourmidyear report.

Figure 2. Regions and industries with the Cring ransomware detections (From January 1 to September 22, 2021)

How to protect systems from ransomware

With ransomware, prevention is one of the most potent forms of protection. A proactive approach such as patching vulnerabilities and monitoring systems for signs of unusual behavior helps curb ransomware before it can cause any real damage to a system.

In the larger scheme of things, coming up with ransomware defense plans will help enterprises know which steps to prioritize. Here are some best practices that follow the lead of frameworks set by theCenter of Internet Security(CIS)and theNational Institute of Standards and Technology(NIST):

  • Audit events and take inventory.Audit both event and incident logs to spot suspicious behavior.Take note of all assets and data. Identify authorized and unauthorized devices and programs.
  • Configure and monitor.Manage hardware and software configurations. Only grant administrative privileges when necessary.
  • Patch and update.Conduct regular vulnerability assessments and patching or virtual patching for operating systems and programs. Update software and applications.
  • Protect systems and recover data.Administer data protection, backup, and recovery measures. Implement multifactor authentication (MFA).
  • Secure and defend layers:Perform sandbox analysis to filter malicious emails. Employ security solutions to all layers of the system such as email, endpoint, web, and network.
  • Train and test.Conduct regular training and security skills assessment for employees. Perform red-team exercises and penetration tests.

Trend Micro solutions

Organizations can benefit from multilayered protection (for layers such as endpoint, email, web, and network) with security solutions that can detect malicious components and help monitor concealed malicious behaviors in the system.

Trend Micro Vision One™spots suspicious behaviors that might seem insignificant when observed from only a single layer.Trend Micro Apex One™protects endpoint devices through automated threat detection and response against ransomware, fileless threats, and other advanced concerns.

Trend Micro Cloud One™ Workload Securitydefends systems against threats that exploit vulnerabilities. This is done through virtual patching, machine learning (ML), and harnessing the latest in global threat intelligence.

Trend Micro™ Deep Discovery™ Email Inspectoremploys custom sandboxing and advanced analysis techniques to effectively block ransomware before it gets into the system, since one of the ways ransomware spreads is through malicious emails.

Indicators of Compromise (IOCs)

SHA-256
Trend Micro Pattern Detection
f7d270ca0f2b4d21830787431f881cd004b2eb102cc3048c6b4d69cb775511c8
Ransom.MSIL.CRYNG.A
e687308cd4184e17c33fa9e44686e7d6a4d73adf65f7fb3cac9c4ad765b4ffdf
Ransom.Win32.CRING.C
771a680f9a09a7a73ac2678f31f4d82fce49c046cc5f4c415cea5310b833911f
Trojan.BAT.DISABLER.AA
71821ddb0b49f5b91fc520ca3de1c5ea7cee3bf166ddebd625859966fc5221a2
Trojan.BAT.CRING.A
a999e096a9fb6a994f4d58b04001c61bb2d1fd0d4f0fa87a5be0b61b23591f24
Trojan.PS1.COBEACON.FAIN

MITRE ATT&CK Tactics and Techniques

Tactic
Technique
Initial access
T1078: Valid Accounts
T1190: Exploit Public-Facing Application
Execution
T1059: Command and Scripting Interpreter
Persistence
T1546.012: Event Triggered Execution: Image File Execution Options Injection
Privilege Escalation
T1078.002: Valid Accounts: Domain Accounts
Defense Evasion
T1562.001: Impair Defenses: Disable or Modify Tools
T1070.004: Indicator Removal on Host: File Deletion
Credential Access
T1003: OS Credential Dumping
T1552: Unsecured Credentials
Discovery
T1083: File and Directory Discovery
Lateral Movement
T1570: Lateral Tool Transfer
T1105: Remote File Copy
T1021: Remote Services
Command and Control
T1090: Proxy
T1105: Ingress Tool Transfer
T1043: Commonly Used Port
T1188: Multi-hop Proxy
T1094: Custom Command and Control Protocol
Exfiltration
T1041: Exfiltration Over C2 Channel
Impact
T1486: Data Encrypted for Impact
T1489: Service Stop
T1485: Data Destruction
T1490: Inhibit System Recovery