Protect Your Network. Strategies to Defend Against Clop Ransomware Attacks

Facing Clop ransomware means grappling with encrypted files and ransom demands. Recognized for its substantial impact and complex evasion tactics, understanding and mitigating Clop is critical. Our article provides insights into its operations and practical defenses to help you prepare against this cybersecurity challenge.

Key Takeaways

  • Clop ransomware is financially motivated, often demanding high ransoms and has extorted over $500 million since it emerged in 2019, focusing on disabling security measures and leaking sensitive data if demands are not met.

  • Sophisticated tactics are used by Clop ransomware to maintain persistence and evade detection, including exploiting vulnerabilities, manipulating processes, and using tools like Cobalt Strike and FlawedAmmyy RAT for lateral movement within networks.

  • Defensive strategies against Clop ransomware include strengthening email and endpoint security, network defenses, regular backups, incident response planning, dark web monitoring, and staying informed on the latest IOCs and detection strategies.

Decoding the Clop Ransomware Threat

Illustration of a computer with a ransomware alert on the screen

Emerging in 2019 and targeting a range of Windows operating systems, Clop ransomware has steadily climbed the ranks of the underworld of ransomware gangs. Derived from the Russian word for ‘bed bug’, Clop symbolizes stealth, evading detection by disabling Windows Defender and Microsoft Security Essentials. The ransomware targets organizations with sizeable budgets, threatening to leak sensitive data and demanding high ransoms, with some reaching up to $20 million.

The criminal malware distribution has been lucrative, with Clop successfully extorting more than $500 million from various victims, including those in the energy sector and academic institutions.

The Evolution of Clop Ransomware

The Clop ransomware gang’s ability to evolve showcases the adaptability of ransomware actors. Since its inception as a Ransomware-as-a-Service (RaaS) operation in 2019, Clop has become known for its ever-changing tactics, techniques, and procedures (TTPs). The ransomware has seen several variants, each demonstrating increased technical sophistication in delivery methods. These variants are often identified by unique changes in their file extension names such as:

  • ‘CIIp’

  • ‘.Cllp’

  • ‘.CL_O_P’

  • ‘ClopReadMe.txt’

  • ‘READ_ME!!!.TXT’

How Clop Ransomware Infects Systems

A range of methods are employed by Clop ransomware to infiltrate systems. These methods include:

  • Phishing campaigns, that utilize malicious links disguised as legitimate communication

  • Spam emails with HTML attachments, often deployed by the TA505 group

  • Spam email attachments

  • Trojans

  • Hyperlinks

  • Software cracks

  • Unprotected Remote Desktop Protocol (RDP) connections

  • Compromised websites

Once inside a system, Clop solidifies its infection by issuing a fraudulent certificate to the executable and initiating a batch file that alters and overwrites system files.

The Business Model: Extortion and Data Auctions

Clop ransomware operators exploit the fear of data exposure by using a variety of extortion techniques. From sending ransom notes to upper management to quadruple extortion involving threats of:

  • auctioning off stolen information

  • publicizing stolen information

  • releasing the stolen data on their data leak site

  • posting the stolen data on underground forums, aiming to steal data from even more victims

The Clop gang knows how to apply pressure. If victims fail to meet their ransom demands, Clop threatens to auction or release the stolen data, adding to the victims’ woes.

The group’s approach has shown adaptability, shifting tactics from deploying ransomware to focusing on data exfiltration and subsequent extortion, possibly in response to increasing law enforcement pressure.

Anatomy of a Clop Attack

Illustration of a hacker gaining unauthorized access to a network

To develop effective defense strategies, it’s vital to understand the anatomy of a Clop attack. Clop ransomware attacks follow a series of steps, from initial access to sustaining presence and lateral movement, all the way to encryption and demands. Each stage involves a set of tactics designed to infiltrate, exploit, and ultimately exfiltrate sensitive data.

Initial Access Tactics

Phishing campaigns are the primary means through which Clop ransomware spreads, using malicious email attachments or links to deceive users and gain initial system access. Spear-phishing emails and compromised Remote Desktop Protocol (RDP) connections are among the initial access tactics used by the Clop ransomware group, often involving brute-forced passwords or exploiting existing vulnerabilities.

In addition to these methods, Clop has been known to exploit zero day vulnerability in software such as MOVEit to gain initial access to various global companies. The cybercriminal group FIN7 has utilized the POWERTRASH malware and the Lizar toolkit in conjunction with Clop, enabling the launch of ransomware attacks on compromised computers.

Sustaining Presence and Lateral Movement

Once initial access is gained, the initial access broker utilizes Clop ransomware, employing a variety of tactics to maintain presence and navigate laterally within the compromised system. It scans for workgroup information to differentiate personal computers from corporate ones, indicating a targeted strategy to infiltrate enterprise networks. The compromised Active Directory server is then exploited for both reconnaissance and to attack other machines within the network.

For lateral movement, Clop employs tactics such as:

  • Exploiting SMB/Windows admin shares

  • Using tools like Cobalt Strike

  • Deploying malware like FlawedAmmyy RAT and SDBOT to spread the infection and execute the ransomware on target machines.

Encryption and Demands

File encryption and the presentation of ransom demands comprise the final stages of a Clop attack. Clop ransomware encrypts files using a combination of ciphers, primarily the AES cipher, and appends file extensions such as .CLOP or .CIOP to render data inaccessible. Upon completion of file encryption, victims are presented with a ransom note that provides instructions for payment, often requiring transactions in cryptocurrencies like Bitcoin.

The ransom notes left by Clop ransomware typically include threats of permanent data deletion or the publication of sensitive information if the ransom is not paid, adding pressure on the victims to comply with the demands.

Global Impact: Regions and Industries Under Siege

Photo of a global map with highlighted regions affected by ransomware attacks

Certain industries and regions bear the brunt of Clop ransomware attacks, causing a global impact. The ransomware has predominantly targeted the following industries:

  • Banking

  • IT

  • Healthcare

  • Finance

  • Professional services

  • Retail

Geographically, North America and Europe emerged as the most affected regions, with the United States, the United Kingdom, and Canada being the most targeted countries.

High-Risk Industries

Due to their substantial financial resources and the nature of their data, certain industries face a higher risk of Clop ransomware attacks. The primary industries targeted by Clop ransomware include:

  • IT

  • Healthcare

  • Finance

  • Professional services

  • Retail

Clop has shown a preference for victims with significant financial resources to pay ransoms, targeting organizations rather than individual users.

High-profile companies are particularly attractive targets for ransomware groups, such as the Clop ransomware gang, as they often have compromised corporate networks.

Geographical Hotspots for Clop Attacks

From January to May 2023, North America and Europe have been identified as the regions most impacted by Clop ransomware. The majority of Clop ransomware attacks during this time targeted organizations in North America, with 64 organizations compromised. The United States, the United Kingdom, and Canada top the list for the highest number of organizations impacted by Clop ransomware in these regions.

Beyond North America and Europe, countries such as Australia, Colombia, India, and Mexico have also been among the most targeted by the Clop ransomware group.

Protecting Your Infrastructure: Mitigation and Defense

Illustration of a shield protecting against ransomware attacks

Despite the significant threat of Clop ransomware, organizations can utilize various strategies to protect their infrastructure and lessen the potential attack’s impact. These strategies include:

  • Strengthening email and endpoint security

  • Enhancing network defenses

  • Implementing regular backups

  • Developing an incident response plan

By implementing these measures, organizations can improve their security posture and reduce the risk of falling victim to Clop ransomware.

Strengthening Email and Endpoint Security

Strengthening email and endpoint security serves as the first line of defense against Clop ransomware. This includes deploying cloud-based email security solutions providing multi-layered protection including anti-spam, anti-malware, and phishing detection. Implementing email authentication techniques like SPF, DKIM, and DMARC can prevent spoofing and phishing.

On the endpoint side, EPP or EDR solutions can be installed for monitoring and managing security on all network endpoints. Employee training on safe web surfing, password strength, and the importance of maintaining updated systems is also crucial in defending against Clop ransomware attacks.

Enhancing Network Defenses

Enhancing network defenses is vital for combating Clop ransomware. Here are some strategies to consider:

  1. Strengthen email and endpoint security.

  2. Implement network segmentation to enhance containment of threats and restrict their spread.

  3. Use firewalls as a robust first line of defense, filtering and blocking suspicious external traffic and data packets that may carry ransomware.

Intrusion detection and prevention systems can continuously monitor network traffic for abnormal activity, enabling timely detection of potential ransomware attacks. Integrating threat intelligence platforms can leverage up-to-date information about emerging ransomware campaigns and their indicators of compromise, equipping defense mechanisms with tailored, actionable data. Collaborating with an infrastructure security agency can further enhance these protective measures.

Regular Backups and Incident Response Planning

The impact of a Clop ransomware attack can be significantly reduced by implementing regular backups and incident response planning. Regular backups of critical data should be stored offline or in a separate environment immune to ransomware. An incident response plan detailing roles, responsibilities, and communication protocols can help manage a potential breach effectively.

Cyber insurance policies that offer coverage for ransomware attacks, including response services and potentially covering ransom payments, should also be considered.

Technical Breakdown: Tools and Techniques Used by Clop

Illustration of malware and hacking tools used by ransomware groups

To carry out its malicious activities, the Clop ransomware gang employs a sophisticated arsenal of tools and techniques. These range from various malware types to exploits in the wild, and evasion and persistence techniques that make it a formidable adversary in the cyber threat landscape.

Malware Arsenal

Clop’s malware arsenal includes:

  • Get2 loader


  • FlawedAmmyy RAT

  • Cobalt Strike

  • Various web shells such as DEWMODE and LEMURLOOT

The FlawedAmmyy Remote Access Trojan, also known as FlawedAmmyy RAT, is a type of remote access trojan deployed by Clop to collect information and enable communication with the command-and-control server for downloading additional malware components. The SDBOT RAT, part of Clop’s toolkit, can spread by exploiting vulnerabilities and can transfer itself onto removable drives and network shares.

In post-exploitation stages, Clop uses Cobalt Strike for maintaining persistent access and for facilitating lateral movement across the network.

Exploits in the Wild

In the wild, Clop has been known to exploit a variety of vulnerabilities. Some notable exploits include:

  • A previously unknown SQL injection vulnerability, CVE-2023-34362, in Progress Software’s MOVEit Transfer

  • The SolarWinds Serv-U product vulnerability identified as CVE-2021-35211

  • Multiple zero-day vulnerabilities in Kiteworks’ FTA

Web shells like DEWMODE and LEMURLOOT are instrumental for Clop’s persistent access, allowing execution of OS commands, stealing data, creating backdoor accounts, and manipulating Azure system settings.

Evasion and Persistence

To maintain its presence on a compromised system and to evade detection, Clop ransomware employs several techniques, including:

  • Using digitally signed binaries

  • Manipulating processes in Windows environments to bypass detection by security software

  • Achieving persistence by making registry entries, creating startup scripts, modifying domain policies

  • Employing techniques such as process injection and application shimming

These techniques allow the ransomware to stay hidden and continue its malicious activities.

These evasion techniques and persistence strategies make Clop a persistent threat to any organization.

Responding to the Threat: Law Enforcement and Industry Efforts

Law enforcement and industry efforts have crucially disrupted the operations of the Clop ransomware gang in response to its growing threat. These efforts include operations that have led to arrests and takedowns, as well as public-private partnerships that have combined expertise and resources to combat the threat.

Arrests and Takedowns

Operation Cyclone, a transcontinental law enforcement operation coordinated by INTERPOL, targeted the Clop ransomware group’s infrastructural capabilities. This operation led to the arrest of six suspects in Ukraine and the seizure of assets including over $185,000 in cash.

These arrests and takedowns demonstrate the global commitment to tackling the threat of Clop ransomware and bring those responsible to justice.

Public-Private Partnerships

Public-private partnerships have also played a crucial role in combating the threat of Clop ransomware. Such partnerships combine the expertise and resources of both sectors to tackle this cyber threat. Private cybersecurity firms have played a key role in analyzing the Clop ransomware and offering mitigation strategies.

Federal agencies, specifically the Federal Bureau, actively work to investigate and disrupt Clop ransomware operations. These joint operations and shared threat intelligence accelerate the detection and response to Clop ransomware attacks.

Insights from Recent Clop Incidents

Valuable insights into the evolving tactics used by attackers have been provided by recent incidents of Clop ransomware. The ransomware has been observed to employ more complex obfuscation techniques to evade detection and enhance the effectiveness of their attacks.

Furthermore, Clop has updated its encryption algorithms, making it more difficult for victims to recover their data without paying the ransom.

Notable Breaches

Several notable breaches caused by Clop ransomware have been reported. Clop ransomware was the second most dominant ransomware group in Q3 2023, targeting many organizations, particularly in the business services sector. The efficient use of exploits by Clop ransomware, such as the incident involving Kiteworks FTA in 2021, resulted in higher average ransom payments.

Prominent companies, including BA and Boots, were impacted when payroll provider Zellis was compromised by Clop ransomware.

Lessons Learned

Recent Clop ransomware incidents have also provided valuable lessons for organizations. Data minimization practices, such as not leaving data on MOVEit after file transfers, resulted in lesser impact from Clop ransomware attacks. Enabling and properly configuring built-in encryption tools, such as MOVEit’s, can sometimes prevent data loss during breaches.

These lessons underscore the importance of preventive measures and detective controls in defending against ransomware attacks.

Indicators of Compromise and Detection Strategies

Protecting against the threat of Clop ransomware necessitates recognizing its indicators of compromise (IOCs) and implementing detection strategies. While actual IOCs can vary between specific incidents, joint advisories detailing IOCs and detection strategies have been released, providing guidance for IT security teams in identifying and responding to Clop ransomware attacks.

Recognising IOCs

The addition of the ‘.Clop’ file extension to encrypted files is a primary indicator of a system affected by Clop ransomware. Other indicators include:

  • Unauthorized use of the wevtutil command, which may reflect Clop ransomware’s attempt to clear Windows Event Logs

  • The deletion or manipulation of shadow copies

  • The resizing of shadow storage

These actions are key indicators of Clop’s attempt to hinder file recovery post-encryption.

The presence of ransom notes with filenames like ‘ClopReadMe.txt’ on the infected system is a strong indicator of a Clop ransomware attack.

Implementing Detection Mechanisms

Effective detection mechanisms are crucial in identifying and mitigating Clop ransomware attacks. Information-sharing partnerships such as the Cyber Security Information Sharing Partnership (CiSP) can keep organizations updated on new ransomware threats including Clop indicators of compromise. Implementing detection searches like ‘Suspicious wevtutil usage’, ‘Windows Event Log Cleared’, and ‘Deleting Shadow Copies’ can help detect Clop ransomware.

Tools such as a Splunk Phantom playbook can provide an organized response to Clop ransomware, including:

  • Detonating suspicious file samples

  • Blocking IP addresses and hashes

  • Hunting files

  • Terminating malicious processes

  • Quarantining affected devices.


Clop ransomware represents a significant and evolving cyber threat. Its advanced techniques, focus on high-value targets, and adaptability make it a formidable adversary. However, understanding its tactics, staying abreast of updates, and implementing robust cybersecurity measures can go a long way in mitigating this threat. As the landscape of cyber threats continues to evolve, including the use of the dark web so must our defences. The fight against Clop ransomware, and indeed all forms of cyber threats, requires constant vigilance, collaboration, and innovation.

Frequently Asked Questions

What is the Clop ransomware?

Clop ransomware is a dangerous file-encrypting virus that belongs to the Cryptomix ransomware family and uses the AES cipher to encrypt various types of files.

How can people protect themselves from Clop ransomware?

To protect yourself from Clop ransomware, use comprehensive protection against spam and malicious links, and regularly back up important files to prevent data loss. Be cautious of email attachments from unknown sources.

What companies are affected by the Clop ransomware?

Deloitte, Ernst & Young and PwC are among the companies affected by the Clop ransomware, putting customer data at risk. Other companies have also been targeted by this ransomware.

How does Clop ransomware spread?

Clop ransomware primarily spreads through phishing campaigns utilising malicious attachments or links in emails that appear legitimate, as well as compromised Remote Desktop Protocol (RDP) connections. Avoid clicking on suspicious links or downloading attachments from unknown sources to protect against this.

What industries are most targeted by Clop ransomware?

Clop ransomware primarily targets industries such as IT, healthcare, finance, professional services, and retail. This poses a serious threat to businesses across these sectors.

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