What is Ransomware? Definition, Types & Protection

Ransomware is malicious software designed to encrypt or block access to data until a ransom is paid, typically in cryptocurrency. Modern attacks increasingly involve double extortion, where adversaries steal data before encryption and threaten to publish it if payment is refused. 

Attackers most often gain initial access through phishing emails, stolen or brute-forced credentials, unpatched vulnerabilities or compromised remote services such as RDP. Once they establish a foothold, they deploy ransomware to disrupt operations and pressure organizations into paying. 

According to the 2025 Verizon Data Breach Investigations Report (DBIR), ransomware appeared in 44% of breaches involving malware and 31% of all incidents, continuing its rise as one of the most prominent threats. Stolen credentials remain one of the most common entry vectors. 

A ransomware attack is one of the most critical threats a business can face, with immediate and often devastating consequences: 

• Financial loss: Ransom payments can be substantial. While the DBIR notes the median ransom payment dropped to $115,000, it still represents a major cost. 

• Data theft and exposure: Many ransomware gangs use double extortion: stealing data before encryption to force payment. 

• Operational downtime: Ransomware can disable operations for days or weeks, costing millions. SMBs are hit particularly hard; in DBIR 2025, 88% of small business incidents involved ransomware compared to 39% for large organizations. 

• Reputational damage: Publicly leaked data or service outages erode trust with customers, partners and regulators. 

Most ransomware campaigns follow a predictable lifecycle: 

1. Infection: Attackers deliver ransomware via phishing emails, malicious attachments, cracked software downloads or by exploiting unpatched systems. The DBIR reports that stolen credentials (22%) and exploited vulnerabilities (20%) were top initial access methods in 2024. 
2. Execution: The malware executes silently, encrypting files, disabling backups and sometimes destroying shadow copies. 
3. Extortion: After encryption, a ransom note demands payment and may threaten to release stolen data if the ransom isn't paid. 
4. Remediation: Victims either pay (the DBIR found 64% of victims refuse to pay, although payment rates vary by sector) or restore from clean backups while patching the exploited vulnerability. Speedy detection and backup availability drastically reduce impact. 

Ransomware is not a single program but a collection of families. Explore the major groups: 

• Akira: A newer family targeting enterprises with double-extortion tactics. 

• Ryuk: Known for high-impact campaigns against hospitals and municipalities. Uses manual lateral movement. 

• WannaCry: A worming ransomware that exploited a Windows SMB vulnerability and caused a global outbreak in 2017. 

• Conti: An affiliate-driven franchise famous for rapid encryption and dedicated leak sites. 

• Detection: The key to minimizing damage is early detection. This requires endpoint protection capable of detecting suspicious encryption behavior early in the attack chain. AI-based behavioral detection can monitor processes in real-time to spot and block zero-day strains before they execute. 

• Response: A successful incident response plan includes preparation, immediate isolation of affected systems, forensic investigation, restoration from immutable backups and clear co

• Technical controls: Block the primary initial access vectors. This includes filtering malicious emails, enforcing multifactor authentication (MFA) to neutralize the threat of compromised credentials, and implementing a robust vulnerability assessment and patch management program. Promptly patching unpatched systems reduces the exposed entry points that attackers rely on. 

• Data protection: The most critical defense is maintaining immutable, off-site and tested backups. This ensures you can always restore your data, which eliminates the need to pay a ransom for the encryption. However, it is essential to remember that backups must be isolated. Furthermore, backups alone do not solve the "double extortion" threat, as attackers may still leak the data they exfiltrated before the encryption. 

• Policy: Establish a clear policy before an attack. Law enforcement strongly discourages paying ransoms; it funds criminal activity, marks you as a target and does not guarantee you will get your data back. Organizations must also consult legal counsel to understand the significant compliance consequences, as payments may violate sanctions or other regulations. 

Acronis Cyber Protect Cloud offers multilayered ransomware defense: 

• AI-based behavioral detection: Monitors processes and blocks encryption activities in real time, stopping zero-day strains before they execute. 

• Active anti-malware: Provides continuous scanning and memory inspection to stop known and emerging ransomware. 

• Ransomware rollback and recovery: Allows one-click restoration from immutable, off-site backups, eliminating the need to pay a ransom. 

• Vulnerability assessment and patch management: Reduces exposed entry points by automatically identifying and patching known vulnerabilities. 

• What is Malware?
• What is Social Engineering?
• What are Attack Groups?

What is malware, and how does ransomware differ from other malicious software? 

Malware refers to any software created to disrupt systems, steal information or gain unauthorized access. Ransomware is a specific type of malware that encrypts files and blocks access to data until a ransom is paid. Modern attacks often involve double extortion, where attackers steal data before encryption and later threaten to publish it if the victim does not pay. This combination of disruption and data exposure creates significant risk for security, IT and compliance groups. 

What impact can a ransomware or data extortion incident have on an organization? 

A successful attack can prevent access to the systems and data needed to deliver mission-critical services. Recovery may take days or weeks, which leads to financial losses, operational downtime, customer dissatisfaction, reputational damage and regulatory challenges. The effects often continue long after technical recovery is complete. 

What trends in adversary behavior should organizations be prepared to defend against? 

Ransomware operators increasingly behave like structured and well-resourced businesses. They use automation, AI-generated phishing content and realistic social engineering to improve their success rates. Some attacks progress extremely quickly, with intrusion to lateral movement occurring in under a minute. Many incidents also rely on legitimate tools and stolen credentials, making detection more difficult. 

How does good cyber hygiene reduce ransomware risk? 

Strong cyber hygiene reduces exposure to common attack paths. Practices such as timely patching, strong authentication, removal of unnecessary services and reliable automated backups help protect critical assets. These basics significantly reduce the effectiveness of credential theft and exploitation of unpatched vulnerabilities. 

What is the most important step an organization can take to prepare for a ransomware incident? 

Maintaining encrypted, offline and regularly tested backups is essential for recovery. Because ransomware often targets connected backups, isolating backup copies is critical. Regular testing ensures that data can be restored quickly, and using multiple cloud providers helps avoid vendor lock-in. 

How should organizations manage access control to reduce the risk of compromise and lateral movement? 

Zero trust principles provide strong protection by requiring authentication and validation for every access request. Users should receive only the access needed for their role. Phishing-resistant MFA should be enforced on email, VPNs, privileged accounts and any system that supports sensitive or critical operations. 

What are the best practices for securing remote access services such as RDP and VPN? 

Organizations should limit RDP usage and enforce MFA for all remote access. Unused RDP ports should be closed, login attempts should be monitored and lockout policies should be enabled. VPN appliances and other network infrastructure must be patched promptly because outdated or misconfigured devices are frequently exploited. 

How can organizations protect against ransomware delivered through phishing or social engineering? 

Effective defense combines training with technical controls. Employees should be trained to identify suspicious messages, while email gateways should filter malicious content. Blocking dangerous attachment types, disabling untrusted macros, and enforcing DMARC policies help reduce spoofing and credential theft. 

Why is third-party and MSP risk important in ransomware prevention? 

Many ransomware incidents originate from compromised service providers or vendors. Organizations should verify the security practices of third parties, apply least privilege and separation of duties for their access, and include clear security requirements in contracts. This is especially important when MSPs handle backups or manage critical infrastructure. 

What are the first steps to take when a ransomware incident is detected? 

Teams should activate the incident response plan immediately. They should identify and isolate affected systems to stop the spread. Cloud environments should have snapshots created to preserve evidence. Recovery should begin with the systems identified as most critical in the organization’s asset inventory. 

How can organizations improve detection of sophisticated ransomware threats? 

Centralized logging through a SIEM improves visibility and helps correlate suspicious activity. Teams should watch for signs of precursor malware such as QakBot, Bumblebee or Emotet, which often precede ransomware deployment. EDR tools and application allowlisting increase the likelihood of detecting unauthorized activity before encryption begins. 

What threat-hunting activities are most important during an active incident? 

Threat hunters should look for abnormal account creation or privilege escalation in Active Directory, unusual VPN login activity, and attempts to interfere with backups. They should also check for unauthorized penetration testing tools such as Cobalt Strike or misuse of remote management utilities, since attackers often use these for persistence. 

What does full recovery and eradication require after containment? 

Recovery should involve rebuilding affected systems with approved standard images or infrastructure-as-code templates. Credentials must be reset, vulnerabilities patched, and restored data validated to avoid reinfection. Once recovery is complete, lessons learned should be documented to strengthen future controls and response processes. 

Who should organizations report ransomware incidents to? 

Organizations should follow regulatory guidance and report incidents to CISA, the local FBI field office, IC3 or the United States Secret Service. They should also notify internal leadership, managed security service providers, cyber insurance partners and any other stakeholders identified in the communication plan.