The five most typical types of malware are viruses, worms, trojans, spyware and ransomware.
1. Computer viruses were originally spread through the sharing of infected floppy disks. As technology evolved, so too did the distribution method. Today, viruses are commonly spread through file sharing, web downloads and email attachments.
2. Computer worms have existed since the late 1980s but were not prevalent until networking infrastructures within organizations became common. Unlike computer viruses, worms can crawl through networks without any human interaction.
3. Trojans are designed specifically to extract sensitive data from the network. Many types of Trojans will take control of the infected system, opening up a back door for an attacker to access later. Trojans are often used in the creation of botnets.
4. Spyware is not typically malicious in nature, but it is a major nuisance because it often infects web browsers, making them nearly inoperable. At times, spyware has been disguised as a legitimate application, providing the user with some benefit while secretly recording behaviour and usage patterns.
5. Ransomware is an attack that often encrypts the files on an endpoint or server demanding the end-user to pay a ransom in bitcoin to receive the encryption key. When it spreads to business-critical systems, the cost of the ransom can swell to hundreds of thousands of dollars.
Ensure that your network is protected against all types of malware
All firewalls should safeguard organizations from viruses, worms, trojans, spyware and ransomware.
This is best accomplished by integrating these 
protections into a single-pass, low-latency approach that blocks attack vectors not only at the gateway, but also at endpoints beyond the traditional perimeter. Look for features that include:
• Network-based malware protection to block attackers from downloading or transmitting malware to a compromised system
• Continuous and timely updates to safeguard networks around the clock from millions of new malware variants as soon as they are discovered
• Intrusion prevention service (IPS) to prevent attackers from exploiting network vulnerabilities
• Network sandboxing to send suspicious code to a cloud-based isolated environment for detonation and analysis to find never-before-seen malware