The Raptoric Journal/Offensive Security
Offensive SecurityJun 16, 2026 · 12 min read

Malware: the main types and how to defend against them

Viruses, trojans, ransomware, and spyware are different kinds of malware with the same goal: to compromise your systems. Here is how they differ, how they get in, and how to defend against them.
A security analyst reviewing a malware alert on an endpoint protection dashboard.
Written by
R
Raptoric Offensive Security
Share
LinkedInX / TwitterCopy link

Malware is the collective name for software built to harm a system, steal data, or hand control to an attacker. Viruses, worms, trojans, ransomware, and spyware are different kinds of malware, but their goal is similar: to get into your environment and exploit it. Understanding the main types helps you recognize the threat and put the right defense in place. This post explains the types of malware, how they get in, how to spot an infection, and how to protect yourself.

Detecting and responding to malware is something we build through threat detection and response, and we test your resilience to it through offensive security.

The types of malware

The types differ in how they spread and what they target, but they are often combined.1

TypeHow it works
VirusAttaches to a file and spreads when a user runs it.
WormSpreads across a network on its own, with no user action.
Trojan horsePoses as a useful program while hiding a malicious function.
RansomwareEncrypts data and demands a ransom, often alongside data theft.
SpywareSecretly collects data, passwords, and user habits.
RootkitHides an attacker's presence and maintains persistent access.
BotnetA network of infected devices under an attacker's control.
The most common types of malware.

How malware gets into a system

Almost every infection starts at one of a few predictable entry points, which is exactly where defense has the most effect.

  • Phishing messages with infected attachments or links, the most common entry point.
  • Unpatched vulnerabilities in software and operating systems.
  • Infected USB devices and pirated or fake software.
  • Compromised websites that exploit the browser.
  • Supply chain risk, through compromised software from a vendor.

Signs of an infection

Modern malware tries to stay hidden, but it often leaves traces: a sudden drop in performance, unusual network traffic, unexpected pop-ups, disabled security tools, or files that will not open. Each of these is worth investigating, because early detection limits the damage.

How to protect yourself

Defense is built in layers that together make both entry and spread harder.

  1. 01
    Keep systems updated
    Patch operating systems and applications regularly, because attackers exploit known vulnerabilities quickly.
  2. 02
    Deploy advanced detection
    EDR tools recognize suspicious behavior, not just known signatures.
  3. 03
    Limit privileges
    The principle of least privilege stops an infection on one account from compromising everything.
  4. 04
    Keep backups
    Regular, offline, and immutable backups make recovery possible after an attack.
  5. 05
    Train your people
    Most infections start with a human action, so training against phishing has a large effect.

How Raptoric helps

We help companies detect and stop malware before the damage grows, through threat detection and response, and we verify resilience through penetration testing. Book a scoping call.

Frequently asked questions

What is the difference between a virus and a trojan?
A virus attaches to a file and spreads when a user runs it. A trojan horse poses as a useful program while hiding a malicious function. A trojan does not need to spread on its own; it relies on the user installing it.
Is antivirus enough?
Antivirus is useful but not enough on its own. Modern malware evades signature-based detection, so you also need advanced detection (EDR), updates, access control, backups, and training.
How do I spot an infection?
Signs include a sudden drop in performance, unusual network traffic, pop-ups, disabled security tools, and files that will not open. Each sign is worth investigating, because early detection limits the damage.
How does malware spread most often?
Most often through phishing with infected attachments or links, unpatched vulnerabilities, and infected files. Supply chain risk through vendor software is increasingly common too.

Sources

  1. 1ENISA. ENISA Threat Landscape. European Union Agency for Cybersecurity, 2024. Link
  2. 2CISA. Malware, Phishing, and Ransomware. Cybersecurity and Infrastructure Security Agency, 2024. Link
Want this tested on your own systems?
Our team will scope it with you on a 30-minute call.
Book a scoping call
Keep reading
All insights →