Understanding and defending against malware: The practical guide for businesses

What is malware – and why is it dangerous?

Malware is short for “malicious software” and refers to programs that have been developed to damage, manipulate, or spy on IT systems.

The aim of such software is to gain unauthorized access to data, paralyze systems, or blackmail users. Malware can cause considerable damage on both private devices and company networks. There are different types of malware, including viruses, worms, Trojans, ransomware, and spyware, each with its own mechanisms and objectives. It is often spread unnoticed, for example via infected email attachments, manipulated websites or compromised software downloads. Attacks using malware are now often automated and professionally organised. They are among the most common and serious forms of cyber attacks worldwide. A comprehensive understanding of malware and how it works is therefore essential in the context of cyber attacks.

Consequences of a malware attack

A malware attack can have serious consequences for companies. Common consequences include the loss of sensitive data, business interruptions, or the compromise of entire networks. Ransomware can encrypt critical systems and make companies vulnerable to extortion.
In addition, there is the threat of high costs for recovery, forensic analysis, and potential contractual penalties for non-compliance with legal obligations.
The damage to reputation is also considerable: customers, partners, and investors quickly lose trust. The situation becomes particularly critical if personal data is affected by the attack—in which case fines under the GDPR may also be imposed.
Malware attacks therefore not only compromise IT security, but also the economic and legal stability of a company.
 

How does malware get into my company?

Malware usually enters a device via seemingly harmless files or links. Common infection vectors include email attachments, malicious downloads, manipulated websites, or compromised software updates. USB sticks and other external storage media can also transmit malware. Malware often disguises itself as a legitimate file or application and is activated by the user without their knowledge. In corporate networks, attackers also use targeted phishing campaigns or exploit security vulnerabilities in outdated software. Once a device is infected, the malware can spread throughout the network. Regular updates, security solutions, and vigilant user behavior are crucial for detecting and blocking such infection routes at an early stage.
 

Protection against malware

Effective protection against all types of malware starts with a comprehensive security strategy. Companies must consider technical, organizational, and human factors equally to minimize vulnerabilities. This involves not only the use of security software, but also clear processes, regular training, and strong security awareness throughout the organization.

10 tips for protecting against malware:

• Establish patch management
  Implement centralized patch management to promptly close vulnerabilities in operating systems and applications. Solutions such as Microsoft WSUS, Ivanti Patch Management, or automated endpoint tools can help with implementation.
• Use endpoint detection & response (EDR) and firewall solutions
  Use modern security solutions such as EDR systems (e.g., CrowdStrike, SentinelOne, Sophos Intercept X) and next-generation firewalls (e.g., Fortinet, Palo Alto) to protect against known and unknown malware.
• Use email gateways with threat protection
  Rely on email security solutions such as Proofpoint, Barracuda, or Microsoft Defender for Office 365 to filter phishing emails, malicious attachments, and links at an early stage.
• Implement guidelines for download and application control
  Prevent the use of unauthorized software through application whitelisting (e.g., Microsoft AppLocker) and controlled software distribution via central IT systems.
• Implement role-based access control (RBAC)
  Consistently implement the principle of least privilege, e.g., through identity and access management (IAM) solutions such as Okta, One Identity, or Microsoft Entra ID (formerly Azure AD).
• Pursue a zero trust strategy
  Do not trust any device or user per se. Check every access contextually and dynamically – supported by solutions such as Zscaler, Cisco Zero Trust, or Microsoft Zero Trust Framework.
• Plan business continuity and disaster recovery
  Create emergency and recovery plans with regular offsite backups. Solutions such as Veeam, Acronis, or Rubrik back up business-critical data redundantly and in an audit-proof manner.
• Conduct security awareness training
  Train employees regularly on phishing, social engineering, and safe behavior. Tools such as KnowBe4, SoSafe, and Awareness Hero offer scalable training platforms for companies.
• Implement network segmentation and microsegmentation
  Logically separate sensitive systems from each other – e.g., through VLANs, SDN technologies, or microsegmentation using VMware NSX or Cisco ACI – to prevent lateral movement by attackers.
• Introduce security information and event management (SIEM) and monitoring
  Use SIEM systems such as Splunk, QRadar, or Microsoft Sentinel to detect anomalies and threats and analyze suspicious activity in real time.

Malware attacks can never be completely ruled out, but with consistently implemented protective measures, companies can significantly reduce the risk and strengthen their defenses in the long term.
 

Recognizing a malware infection

A malware infection often goes unnoticed – but there are typical signs that users should look out for.

Unexpected system slowdowns, frequent crashes, or programs that open on their own can be indications.

Unknown processes in the Task Manager, changed file names, or missing access rights also indicate an infection. 

If passwords suddenly change or emails are sent without your intervention, there is urgent cause for suspicion. 

Victims of a malware attack often also notice unusual network traffic or blocked security functions. 

The earlier such anomalies are detected, the better the consequential damage can be limited. Regular system checks help to detect infections at an early stage.

Malware is just one of many threats in the digital world. Find out how you can protect your company comprehensively against cyberattacks on our cybersecurity page, which provides background information, best practices, and the latest trends.
 

Types of malware

Malware comes in many different forms, each with its own technology, objectives, effects, and threats. It is crucial for companies to be aware of the most important types so that they can detect attacks early and take appropriate protective measures. Below is an overview of common types of malware.

Adware
Adware displays unwanted advertising, often in the form of pop-ups or banners. It is often installed unnoticed with free software. In addition to being distracting, adware can also spy on user behavior and thus become a threat to data privacy.

Backdoor
A backdoor is a hidden access point to a system that allows attackers permanent access – often undetected by conventional security software. It is often installed by other types of malware to prepare for later attacks.
Malicious cryptomining (cryptojacking)
In cryptojacking, attackers use other people's systems to mine cryptocurrencies without their consent. The infected devices suffer from high utilization, performance degradation, and increased power consumption – a serious problem both economically and technically.

Botnet
A botnet is a network of infected devices (“bots”) that are remotely controlled to carry out mass attacks such as DDoS attacks. Companies often do not notice that their systems have become part of such networks until the damage is done.

Fileless malware
This malware operates exclusively in the working memory and does not leave any files on the hard drive. This allows it to evade many conventional antivirus programs. It exploits legitimate system processes and is particularly difficult to detect and remove.

Fileless malware with LOLBins
This type of malware uses so-called “Living off the Land Binaries” (LOLBins) – legitimate system tools such as PowerShell or WMIC – to execute itself inconspicuously. It leaves no classic traces on the hard drive, bypasses many security solutions, and makes forensic analysis much more difficult.

Exploits
Exploits specifically target vulnerabilities in software or operating systems to inject malicious code. They are often part of automated attacks and are used by attackers to exploit security vulnerabilities before updates are available.

Keyloggers
Keyloggers record keystrokes such as passwords, credit card details, or confidential information. They run unnoticed in the background and pose a particular threat to accounts and identities. They are often introduced via Trojans or phishing.

Living off the Land techniques
LotL attacks use existing system functions and trusted software to execute malware activities without introducing additional files. This often allows them to remain undetected by traditional security solutions. What makes them particularly dangerous is that they appear to be legitimate actions, but are actually part of targeted attacks.

POS malware
This malware targets point-of-sale systems and steals payment data, especially credit card information. POS malware poses a serious risk to customer data, particularly in retail and hospitality.

Ransomware
Hackers use ransomware to encrypt data and then demand a ransom for its release. It is one of the most dangerous forms of malware because it not only blocks data, but also paralyzes business processes and makes companies vulnerable to blackmail.

RAT (Remote Access Trojan)
A Remote Access Trojan (RAT) allows attackers to completely control a system remotely. This enables them to steal data, manipulate files, or install additional malware – usually without the victim noticing.

Rootkit
Rootkits give attackers deep control over a system and hide their activities from security programs. They are difficult to detect and are often used to permanently hide other malware.

Scareware
Scareware imitates security warnings to trick users into installing supposed protection software. In reality, these are malicious programs or paid software with no useful function – their sole purpose is to exploit fear.

Spyware
Spyware secretly monitors users' behavior, collects data, and forwards it to third parties. It poses a threat to privacy, is often bundled with harmless-looking software, and remains active for long periods of time without being detected.

Trojans
Trojans disguise themselves as useful programs but contain hidden malicious functions. They often open the door to further malware, such as backdoors or keyloggers, and are considered particularly malicious because they deceive users.

Viruses
A computer virus spreads by attaching itself to other files and replicating itself when they are executed. The virus can delete or modify files or disrupt programs – often at a high rate of propagation.

Worms
Worms spread independently across networks without any action on the part of the user. They can cause enormous damage by blocking resources or downloading additional malware. Their rapid spread makes them particularly dangerous.

Zero-day exploits
Zero-day exploits take advantage of previously unknown vulnerabilities in software or operating systems—i.e., security gaps for which no patch yet exists. Attackers can compromise systems before manufacturers can respond. These exploits are particularly valuable and are often used in targeted attacks.
 

Conclusion

Malware remains one of the biggest threats to businesses – it comes in many forms and is often difficult to detect. Understanding the mechanisms, attack vectors, and protective measures can significantly reduce risks. A holistic security approach is crucial: technical, organizational, and human. Stay alert, raise awareness among your team, and invest in robust IT security structures—because cyber threats are constantly evolving.
 

FAQs about malware

Why is malware distributed?

Malware of all kinds is distributed for a variety of reasons—mostly financial gain. Cybercriminals want to steal data, demand ransom, or exploit resources such as computing power. Some actors also pursue political or ideological goals, such as espionage or sabotage. Selling stolen information on the black market is also a common motive.

Is malware the same as a virus?

Not quite. A virus is a subtype of malware, i.e., a specific form of malicious software. While malware is a collective term for all harmful programs, viruses specifically refer to programs that spread themselves by attaching themselves to other files and activating when they are opened.

Can smartphones be infected with malware?

Yes, smartphones are also vulnerable to malware. Infection often occurs via manipulated apps, phishing messages, or unsecure Wi-Fi networks. Mobile malware can steal data, monitor devices, or incur costs without being noticed. It is particularly dangerous if security updates are missing or users install apps from unsecure sources.

Can Macs be infected with malware?

Macs are not immune to malware, even though they are less frequently targeted than Windows systems. Attackers are increasingly developing malware specifically for macOS. Phishing, adware, and Trojans in particular can also cause damage on Apple devices. It is therefore important to keep your Mac up to date and use security solutions.