How can Ransomware Spread Through a Network?

Ransomware attacks have become one of the most prevalent and damaging cybersecurity threats in recent years. With high-profile incidents like the WannaCry and NotPetya attacks, ransomware has shown that it can cause widespread disruption and significant financial losses. One question that often arises, indeed one of the most searched phrases on the matter, is “How can ransomware spread through a network?” In this post, I’ll explore some of the mechanisms by which ransomware propagates within networks, the tactics used by adversaries to move laterally, and how to protect against ransomware by protecting against lateral movement and securing privileged and service accounts.

Understanding ransomware propagation

To answer this question, it’s essential first to understand how ransomware operates. Ransomware is a form of malware that encrypts the victim’s files, rendering them inaccessible. The attacker then demands a ransom, usually in cryptocurrency, in exchange for the decryption key. However, ransomware doesn’t stop at merely infecting a single machine. It aims to spread throughout the network to maximize its impact and potential payout.

Lateral movement techniques

Once a ransomware attack has successfully infiltrated an organization, attackers employ various techniques to move laterally within the network. Lateral movement refers to navigating from one compromised system to another, typically to escalate privileges and gain access to sensitive information or systems.

1. Exploiting known vulnerabilities: Bad actors often rely on known software vulnerabilities to compromise additional systems within the network. For example, the infamous WannaCry ransomware exploited a vulnerability in Microsoft’s SMB protocol, allowing it to spread rapidly across networks.
2. Pass-the-Hash and Pass-the-Ticket attacks: These attacks involve the theft of hashed user credentials or Kerberos tickets, which can then be used to authenticate to other systems within the network without requiring the user’s password.
3. Credential dumping: By extracting passwords and other credentials from compromised systems, attackers can leverage them to access other parts of the network. Tools like Mimikatz are often employed in this process.
4. Phishing and social engineering: While not technically a lateral movement technique, phishing campaigns, and social engineering can be used to compromise additional user accounts within the organization, granting the attacker access to more systems and potentially facilitating lateral movement.

The importance of service and privileged accounts

One of the key objectives for adversaries in a ransomware attack is to gain access to service and privileged accounts, as these accounts often have elevated permissions and can provide the attacker with the means to compromise additional systems and resources. Once the attackers find these accounts, they can use them to deploy ransomware payloads, exfiltrate sensitive data, or perform other malicious actions.

For example, during the NotPetya attack, the ransomware leveraged the stolen credentials of a privileged account to propagate through the victim’s network. This allowed the ransomware to encrypt files on a large number of systems, significantly increasing the impact and potential payout of the attack.

Securing service and privileged accounts

As demonstrated by many real-world examples, securing service and privileged accounts is essential in mitigating the risk of ransomware attacks. Here are a few best practices to consider:

1. Lockdown lateral movement: Production applications are often vulnerable to security breaches that can have severe consequences. Unfortunately, many current tools lack the ability to fully comprehend application behavior, interactions, and service account activities. To combat this, investigate tools that protect against lateral movement by implementing microsegmentation, using host firewalls, deactivating compromised credentials, and preventing the execution of suspicious command line arguments.
2. Implement least privilege: Ensure that users and services only have the minimum level of access required to perform their tasks. This reduces the potential impact of a compromised account.
3. Use strong, unique passwords: Encourage employees to use complex, unique passwords for their accounts, and require regular password changes. This can help prevent unauthorized access due to credential theft or reuse.
4. Enable multi-factor authentication (MFA): Require MFA for privileged and service accounts to add an additional layer of security, making it more challenging for attackers to compromise these accounts.
5. Monitor and audit account activity: Regularly review and monitor the activity of service and privileged accounts to detect any unusual or suspicious behavior. Implementing a Security Information and Event Management (SIEM) solution can help automate this process and provide real-time alerts.
6. Secure remote access: Implement secure remote access solutions, such as VPNs or Zero Trust architectures, for employees and third-party vendors to minimize the risk of unauthorized access.
7. Educate and train employees: Conduct regular security awareness training for all employees, emphasizing the importance of recognizing phishing attempts, reporting suspicious activity, and adhering to security policies.
8. Keep systems and software up-to-date: Regularly patch and update software, operating systems, and firmware to address known vulnerabilities that could be exploited by ransomware and other threats.
9. Conduct regular risk assessments: Regularly assess your organization’s security posture and identify any vulnerabilities or weaknesses in your network that could be exploited by ransomware or other threats. This will help you prioritize your security efforts and investments.

Understanding how ransomware spreads through a network is crucial for defending your organization against these increasingly sophisticated and damaging attacks. By exploring the techniques attackers use to move laterally within networks, the importance of securing service and privileged accounts, and implementing best practices to protect your organization, you can reduce the risk of ransomware attacks and minimize their potential impact.

In conclusion, answering the question “How can ransomware spread through a network?” requires a comprehensive approach to cybersecurity that addresses the various tactics attackers use to compromise and traverse networks. By implementing a robust security posture and continuously monitoring and updating your defenses, you can better protect your organization from the ever-evolving threat landscape.