Ransomware is malware designed to deny a user or organization access to files on their computer. By encrypting these files and demanding a ransom payment for the decryption key, these malware place organizations in a position where paying the ransom is the easiest and cheapest way to regain access to their files. Some variants have added additional functionality – such as data theft – to provide further incentive for ransomware victims to pay the ransom.
Ransomware has quickly become the most prominent and visible type of malware. Recent ransomware attacks have impacted hospitals’ ability to provide crucial services, crippled public services in cities, and caused significant damage to various organizations.
The modern ransomware craze began with the WannaCry outbreak of 2017. This large-scale and highly-publicized attack demonstrated that ransomware attacks were possible and potentially profitable. Since then, dozens of ransomware variants have been developed and used in a variety of attacks.
The COVID-19 pandemic also contributed to the recent surge in ransomware. As organizations rapidly pivoted to remote work, gaps were created in their cyber defenses. Cybercriminals have exploited these vulnerabilities to deliver ransomware, resulting in a surge of ransomware attacks. In Q3 2020, ransomware attacks increased by 50% compared to the first half of that year.
Dozens of ransomware variants exist, each with its own unique characteristics. However, some ransomware groups have been more prolific and successful than others, making them stand out from the crowd.
Ryuk is an example of a very targeted ransomware variant. It is commonly delivered via spear phishing emails or by using compromised user credentials to log into enterprise systems using the Remote Desktop Protocol (RDP). Once a system is infected, Ryuk encrypts certain types of files (avoiding those crucial to a computer’s operation), then presents a ransom demand.
Ryuk is well-known as one of the most expensive types of ransomware in existence. Ryuk demands ransoms that average over $1 million. As a result, the cybercriminals behind Ryuk primarily focus on enterprises that have the resources necessary to meet their demands.
The Maze ransomware is famous for being the first ransomware variant to combine file encryption and data theft. When targets started refusing to pay ransoms, Maze began collecting sensitive data from victims’ computers before encrypting it. If the ransom demands were not met, this data would be publicly exposed or sold to the highest bidder. The potential for an expensive data breach was used as additional incentive to pay up.
The group behind the Maze ransomware has officially ended its operations. However, this does not mean that the threat of ransomware has been reduced. Some Maze affiliates have transitioned to using the Egregor ransomware, and the Egregor, Maze, and Sekhmet variants are believed to have a common source.
Sodinokibi (also known as REvil) is another ransomware variant that targets large organizations. It has competed with Ryuk over the last several years for the title of the most expensive ransomware variant. Sodinokibi is known to have demanded $800,000 ransom payments.
While Sodinokibi began as a traditional ransomware variant, it has evolved over time. In recent years, it has followed in Maze’s footsteps to include data theft as part of its capabilities. Sodinokibi is known to exploit vulnerabilities in Pulse Connect Secure VPN and Oracle WebLogic servers.
LockBit is a data encryption malware in operation since September 2019 and a recent Ransomware-as-a-Service (RaaS). This piece of ransomware was developed to encrypt large organizations rapidly as a way of preventing its detection quickly by security appliances and IT/SOC teams.
In March 2021, Microsoft released patches for four vulnerabilities within Microsoft Exchange servers. DearCry is a new ransomware variant designed to take advantage of four recently disclosed vulnerabilities in Microsoft Exchange
The DearCry ransomware encrypts certain types of files. Once the encryption is finished, DearCry will show a ransom message instructing users to send an email to the ransomware operators in order to learn how to decrypt their files.
In order to be successful, ransomware needs to gain access to a target system, encrypt the files there, and demand a ransom from the victim.
While the implementation details vary from one ransomware variant to another, all share the same core three stages
Ransomware, like any malware, can gain access to an organization’s systems in a number of different ways. However, ransomware operators tend to prefer a few specific infection vectors.
One of these is phishing emails. A malicious email may contain a link to a website hosting a malicious download or an attachment that has downloader functionality built in. If the email recipient falls for the phish, then the ransomware is downloaded and executed on their computer.
Another popular ransomware infection vector takes advantage of services such as the Remote Desktop Protocol (RDP). With RDP, an attacker who has stolen or guessed an employee’s login credentials can use them to authenticate to and remotely access a computer within the enterprise network. With this access, the attacker can directly download the malware and execute it on the machine under their control.
Others may attempt to infect systems directly, like how WannaCry exploited the EternalBlue vulnerability. Most ransomware variants have multiple infection vectors.
After ransomware has gained access to a system, it can begin encrypting its files. Since encryption functionality is built into an operating system, this simply involves accessing files, encrypting them with an attacker-controlled key, and replacing the originals with the encrypted versions. Most ransomware variants are cautious in their selection of files to encrypt to ensure system stability. Some variants will also take steps to delete backup and shadow copies of files to make recovery without the decryption key more difficult.
Once file encryption is complete, the ransomware is prepared to make a ransom demand. Different ransomware variants implement this in numerous ways, but it is not uncommon to have a display background changed to a ransom note or text files placed in each encrypted directory containing the ransom note. Typically, these notes demand a set amount of cryptocurrency in exchange for access to the victim’s files. If the ransom is paid, the ransomware operator will either provide a copy of the private key used to protect the symmetric encryption key or a copy of the symmetric encryption key itself. This information can be entered into a decryptor program (also provided by the cybercriminal) that can use it to reverse the encryption and restore access to the user’s files.
While these three core steps exist in all ransomware variants, different ransomware can include different implementations or additional steps. For example, ransomware variants like Maze perform files scanning, registry information, and data theft before data encryption, and the WannaCry ransomware scans for other vulnerable devices to infect and encrypt.
Proper preparation can dramatically decrease the cost and impact of a ransomware attack. Taking the following best practices can reduce an organization’s exposure to ransomware and minimize its impacts:
With the high potential cost of a ransomware infection, prevention is the best ransomware mitigation strategy. This can be achieved by reducing the attack surface by addressing:
The need to encrypt all of a user’s files means that ransomware has a unique fingerprint when running on a system. Anti-ransomware solutions are built to identify those fingerprints. Common characteristics of a good anti-ransomware solution include:
A ransom message is not something anyone wants to see on their computer as it reveals that a ransomware infection was successful. At this point, some steps can be taken to respond to an active ransomware infection, and an organization must make the choice of whether or not to pay the ransom.
Many successful ransomware attacks are only detected after data encryption is complete and a ransom note has been displayed on the infected computer’s screen. At this point, the encrypted files are likely unrecoverable, but some steps should be taken immediately:
Check Point’s Anti-Ransomware technology uses a purpose-built engine that defends against the most sophisticated, evasive zero-day variants of ransomware and safely recovers encrypted data, ensuring business continuity and productivity. The effectiveness of this technology is being verified every day by our research team, and consistently demonstrating excellent results in identifying and mitigating attacks.
Harmony Endpoint, Check Point’s leading endpoint prevention and response product, includes Anti-Ransomware technology and provides protection to web browsers and endpoints, leveraging Check Point’s industry-leading network protections. Harmony Endpoint delivers complete, real-time threat prevention and remediation across all malware threat vectors, enabling employees to work safely no matter where they are, without compromising on productivity.