What is Malware? Definition, Types & Protection

Formally, malware (malicious software) refers to any software engineered to damage, disrupt or gain unauthorized access to computer systems or data. Attackers deploy it for various purposes, including data theft, espionage, encrypting files for ransom (ransomware), denial-of-service (DoS) attacks and creating botnets. The growing diversity of malware and the speed at which new strains appear make it a foundational threat to modern digital environments. 

A successful malware infection is not a minor inconvenience; it is a significant business risk that can lead to: 

• Financial loss: This includes direct costs from ransom demands, data-exfiltration penalties and the indirect costs of business interruption. According to Statista, there were 6.06 billion malware attacks globally in 2023. The University of Maryland estimates a cyberattack occurs every 39 seconds, highlighting the immense scale of the problem. 

• Data theft and exposure: Attackers can steal intellectual property (IP), customer records, payment data and trade secrets. This theft can lead to severe compliance fines (e.g., under GDPR or HIPAA) and lawsuits. 

• Operational downtime: Malware can disable critical servers, shut down production lines or destroy vital backups, causing costly and prolonged outages. 

• Reputational damage: A public breach of data or a significant service outage erodes customer trust and investor confidence, causing long-term harm to the brand. 

While different malware families behave in unique ways, most malicious programs follow a similar pattern once they reach a device or network. 

Delivery: Attackers first deliver malware through common vectors such as phishing emails, malicious downloads, compromised websites or exploiting unpatched vulnerabilities. 

Execution and persistence: Once activated, the malware runs on the system, attempts to bypass security controls, and may establish persistence so it can survive reboots or user actions. 

Spread: Many strains attempt to expand their reach, moving laterally, harvesting credentials or probing the network for additional vulnerable systems. 

Impact: Finally, the malware carries out its objective, whether that's encrypting data, stealing information, spying on user activity or enabling remote access. 

Malware is a broad category that covers several distinct families. Key types include: 

• Ransomware: Encrypts a victim's data and demands a payment (ransom) for its release. Phishing is responsible for 54% of ransomware infections and poor cyber hygiene accounts for 27%. 

• Loaders (droppers / downloaders): These are first-stage malware variants whose sole purpose is to install additional, more potent malware (like ransomware or infostealers) on a compromised host. 

• Infostealers: This type of malware is designed to silently harvest and exfiltrate sensitive information from a victim's machine, such as browser credentials, cookies, session tokens and financial data. 

• Remote access trojans (RATs): A RAT provides an attacker with a persistent "backdoor" into a compromised system, granting them complete remote control to steal data, spy on the user or use the machine in a botnet. 

Malware evolves too quickly for signature‑based tools to keep pace. Effective defense relies on behavioral detection and disciplined incident response. 

Modern detection 

• Watch for anomalous behavior: Early signs include unauthorized PowerShell commands, rapid file modifications, unexpected RDP logins and deletion of volume shadow copies. These indicators often surface before encryption or exfiltration begins. 

• Cross‑signal monitoring: Correlate events across endpoints, logs and the network. For example, Windows event logs and Sysmon parent-child process chains can flag suspicious process spawning, while firewall logs reveal outbound connections to unusual IPs. 

• Malware using legitimate services: Recent campaigns like ChaosBot have abused compromised VPN and Active Directory credentials and used WMI to deploy a Rust‑based backdoor. Once installed, ChaosBot side‑loads itself via a legitimate Microsoft Edge component and uses Discord’s API to create a new channel per victim, allowing attackers to send PowerShell commands and receive results. Detecting these threats requires monitoring for unexpected network traffic to collaboration platforms and side‑loaded DLLs. 

Why real‑world examples matter 

• Destructive malware: Wiper families such as WhisperGate, FoxBlade and CaddyWiper have been used in recent geopolitical operations to overwrite system files and boot records. Wipers permanently destroy data and can render recovery impossible. Preparation requires robust, immutable backups and a clear recovery plan. 

• Adaptive backdoors: Sponsor and other backdoors delivered via unpatched Microsoft Exchange vulnerabilities embed configuration files that appear innocuous. These stealth techniques highlight the need for continuous patch management and behavioral analytics.  

Effective response 

• Isolate and contain: Immediately disconnect infected endpoints or segments to prevent lateral movement and preserve forensic evidence. 

• Investigate root cause: Determine how the malware entered: phishing, exploited vulnerability, stolen credentials and close that entry point. 

• Restore from clean backups: Verify the integrity of backups before restoring; wipers can corrupt backups that aren’t protected by immutability and air gapping. 

• Remediate and harden: Apply patches, reset compromised credentials and strengthen controls (e.g., enforce MFA, remove unused services). 

Companies can significantly minimize malware incidents by adopting a layered security (or "defense-in-depth") strategy. 

• Technical controls: Implement robust, modern anti-malware solutions. Enforce strict software patching and vulnerability management to close entry points. Use multifactor Authentication (MFA) everywhere to protect credentials. 

• Network security: Use network segmentation to prevent malware from moving laterally. 

• User training: Conduct regular user training to help employees spot phishing emails and other social engineering tactics. 

• Data protection: Maintain regular, automated and tested backups. This is critical for recovering from destructive malware. 

Defending against modern malware requires multiple, integrated layers. Acronis Cyber

Protect Cloud integrates AI-powered cybersecurity and data protection to stop threats:

• Behavioral detection: Monitors system processes in real-time and stops zero-day malware by identifying suspicious behavior before it can execute and cause damage.

• Active anti-malware: Performs continuous scanning and memory inspection to block known and emerging malware threats, including viruses, trojans and infostealers.

• Ransomware rollback and recovery: For ransomware attacks, Acronis enables one-click restoration of affected files from immutable backups, neutralizing encryption attacks and rendering them ineffective.

See Acronis in Action

• What is Ransomware?
• What is Social Engineering?

What economic and operational impacts can a malware or data extortion incident cause?

A successful infection can halt mission-critical operations by preventing access to systems and data. Organizations often face financial losses, legal liabilities, regulatory penalties, and reputational damage. Downtime and recovery efforts can take days or weeks, and the global scale of cybercrime continues to rise. Industry forecasts estimate that cybercrime costs may reach $10.5 trillion annually by 2025, with malware-driven incidents contributing significantly.

How fast and sophisticated are modern malware campaigns?

Malware operators behave like streamlined businesses. They use automation, cloud infrastructure, encryption and fileless techniques to infiltrate environments quickly. Some threat actors can advance from initial access to internal lateral movement in under a minute. Nearly 80% of observed intrusions now rely on malware-free techniques that abuse legitimate tools, and adversaries increasingly use AI to generate realistic phishing messages or fraudulent websites.

Should an organization ever consider paying an extortion demand?

Security authorities strongly advise against paying. Payment does not guarantee recovery, data deletion, or system integrity. Many organizations that pay still do not regain full access to their data. Paying also incentivizes further attacks and may expose the organization to sanctions or regulatory issues. Executive teams should instead rely on strong preparation, especially tested and isolated backups.

What is the most important technical safeguard for fast recovery from malware?

Maintaining offline, encrypted, and regularly tested backups is essential. Because many malware families attempt to search for and corrupt accessible backups, isolation is critical. Organizations should verify backup integrity frequently and ensure that recovery procedures are well-documented and practiced.

How can we implement access controls that limit malware spread inside the network?

Zero trust architecture provides strong protection by assuming the network may already be compromised. Users and systems must only receive the minimum access required for their roles. Phishing-resistant MFA is essential for email, VPNs and privileged accounts. This approach disrupts lateral movement and reduces the potential blast radius of an infection.

What security controls are recommended for RDP and VPN services?

Remote desktop protocol should be used sparingly. When required, it must be protected with MFA, strict auditing, and network segmentation. Unused RDP ports should be closed, and login attempts should be logged and monitored. VPN appliances must also enforce MFA and remain fully patched, since outdated devices are frequent entry points for malware.

How should organizations manage risk from internet-facing vulnerabilities?

Regular vulnerability scanning and timely patching are essential. Internet-facing systems are frequent targets for automated exploitation. Smaller organizations that struggle withserver maintenance may benefit from migrating email and identity services to reputable managed cloud providers, reducing exposure to unpatched infrastructure.

How can we defend against fileless malware and precursor infections?

Fileless malware operates directly in memory and uses legitimate system tools like PowerShell to execute malicious activity. Organizations should deploy EDR and application allowlisting to restrict unauthorized software execution. Detecting precursor malware, such as QakBot, Bumblebee or Emotet, is critical because these infections often precede large-scale compromises.

What steps help prevent malware delivered through email?

Implement strong email security controls, including DMARC to prevent spoofing, gateway filtering for high-risk indicators and disabling macros in externally sourced Office documents. Because email remains one of the most common delivery methods for malware, these measures significantly reduce exposure.

How does managing third-party and MSP access reduce malware risk?

Threat actors often target service providers to gain access to multiple organizations. Vetting third-party security practices, limiting the scope of their access and enforcing separation of duties help reduce this risk. When MSPs manage backups or critical infrastructure, contractual and technical safeguards must be in place.

What are the first steps teams should take when malware is detected?

Organizations should activate their incident response plan. The initial priority is to identify affected systems and isolate them from the network. Cloud environments should have snapshots taken for investigation. If isolation is not possible, powering down devices may prevent further spread. Teams should then triage systems based on business criticality to determine recovery order.

How can centralized logging improve malware detection and response?

A centralized SIEM platform correlates activity across endpoints, servers, applications and network devices. This visibility helps teams detect suspicious behavior, uncover patterns of lateral movement and determine the scope of an incident. Logs from critical systems should be retained for extended periods to support forensic analysis.

What signs of compromise should threat hunters prioritize?

Threat hunters should search for indicators of unauthorized movement and persistence. These include unusual use of Windows tools that manipulate backups, creation of new privileged accounts, suspicius VPN activity and the presence of remote management or penetration testing tools. Investigators should also look for abnormal outbound traffic that may indicate data exfiltration.

What does effective eradication and recovery look like after containing a malware incident?

Teams should rebuild affected systems with approved, clean images or Infrastructure as Code templates. Credential resets and vulnerability remediation must be completed before systems return to production. Data should only be restored from offline, verified backups to prevent reintroducing the malware. A documented lessons-learned process helps strengthen long-term defenses.

·