7 New and Tricky Types of Malware to Watch Out For

7 New and Tricky Types of Malware to Watch Out For

Malware is a massive threat in the digital world. It can wreck systems, shut down operations, and cost businesses enormous amounts of money. As technology evolves, so do the tactics used by cybercriminals. In 2024 alone, more than 60 million new malware strains were discovered on the internet, and fileless variants were expected to grow another 65%. Analysts estimate AI-assisted malware may make up around 20% of strains in 2025. The volume and the cleverness are both climbing.

Before diving into the seven types, it’s worth drawing a line between two terms people often confuse: malware and ransomware.

Malware vs. Ransomware

Malware is the umbrella term. It means “malicious software” and covers everything from viruses and worms to trojans, spyware, rootkits, and more. Most malware wants to operate in secret. It damages, spies, or steals without drawing attention.

Ransomware is a specific type of malware with a very different personality. Instead of hiding, it announces itself. Locker ransomware locks you out of the entire machine. Crypto ransomware encrypts your files and demands payment for the decryption key. In 2024 the average ransom demand climbed to $2.73 million, nearly $1 million higher than the year before.

Different goals, different playbooks. Knowing which one you’re dealing with helps you respond correctly, and several of the threats below can be used as delivery vehicles for either.

7 Malware Threats to Watch Out For

1. Polymorphic Malware

Polymorphic malware changes its code every time it replicates, which makes traditional signature-based antivirus nearly useless against it. It uses an encryption key to mutate, combining a mutation engine with self-propagating code to continuously morph its appearance.

Internally, it has two main parts: an encrypted virus body and a decryption routine. The body changes shape while the routine stays constant. That balance makes polymorphic malware easier to detect than its cousin metamorphic malware, but still dangerous, since it can evolve into a new version before antivirus signatures catch up.

Attackers use obfuscation techniques like dead-code insertion, subroutine reordering, register reassignment, instruction substitution, code transposition, and code integration. The practical takeaway: you can’t rely on yesterday’s malware signatures. Modern defenses have to include behavioral detection and EDR.

2. Fileless Malware

Fileless malware works without dropping an actual file on the device. Over 70% of malware attacks now involve no file on disk at all. The malicious code runs directly in memory (RAM), which means traditional file-scanning tools have nothing to scan.

It usually starts with a phishing email. The victim clicks a malicious link or opens an attachment, and the payload executes straight into RAM, often exploiting a vulnerability in a document reader or browser plugin to get in.

Once active, fileless malware abuses trusted system tools like PowerShell or Windows Management Instrumentation (WMI) to connect to a remote command and control server. From there it downloads more scripts, exfiltrates data, and moves laterally across the network. Because nothing lands on disk, file-based antivirus is blind to it. This is a big reason modern EDR platforms focus so heavily on process behavior.

3. Advanced Ransomware

Ransomware keeps getting smarter. Today’s variants target not just individual computers but entire networks, using strong encryption and often stealing sensitive data before encrypting it. That double-extortion model adds a second lever: pay up or we leak your data publicly.

A typical attack installs a ransomware agent, encrypts critical files and attached file shares, then displays a ransom note with payment instructions. If victims pay, they’re promised a decryption key. Sometimes it works. Often it doesn’t.

Healthcare systems, manufacturers, and critical infrastructure have become frequent targets because downtime is so painful that paying starts to look rational. It usually isn’t. Offline, immutable backups and a tested recovery plan are the real answer.

4. Social Engineering Malware

Social engineering malware tricks people into installing it by pretending to be something safe. It arrives in emails or messages that look legitimate but aren’t. This category relies on human mistakes rather than technical flaws, which is why it’s so effective.

The pattern usually has four steps: gather information about the target, establish trust by impersonating a known contact or brand, exploit that trust to extract credentials or get a payload executed, and then carry out the real goal, whether that’s account takeover, wire fraud, or planting another piece of malware.

5. Rootkit Malware

A rootkit is a program (or a set of tools) that gives attackers remote, privileged control of a system. Most rootkits are installed to open a backdoor, disable defenses, and set the stage for additional attacks.

Rootkits try hard to avoid detection. They disable endpoint antimalware, hide their own processes, and modify system configurations to stay invisible. They’re commonly delivered through phishing or social engineering. Once installed, they can plant viruses, ransomware, keyloggers, or whatever else the attacker wants next, and they’re notoriously hard to remove cleanly.

6. Spyware

Spyware silently collects data about you and sends it to a third party. It can log keystrokes, take screenshots, track browsing, and harvest login credentials and credit card numbers. Performance suffers, because spyware consumes CPU, memory, and network resources to do its job.

Delivery vectors include app install packages (especially free utilities from sketchy sources), malicious websites, and infected email attachments. On phones, spyware often hides inside apps that look legitimate until they request excessive permissions.

7. Trojan Malware

Trojan malware hides inside what looks like a harmless program. Trojans don’t self-replicate, so most attacks start by tricking the user into downloading, installing, and running the malware themselves.

Once active, Trojans can delete files, install more malware, modify data, steal personal information, and send emails or texts from your accounts. They spread primarily through phishing campaigns that use convincingly spoofed business email addresses, fake invoices, and fake shipping notifications.

How Malware Gets In

Malware and ransomware share the same common entry points:

• Email attachments, especially Office documents, PDFs, and ZIP files.
• Phishing links that lead to fake login pages or drive-by downloads.
• Malicious or compromised websites.
• Infected USB drives, still a surprisingly effective vector.
• Outdated software with unpatched vulnerabilities.

Signs You May Already Have an Infection

Modern malware is built to stay hidden, but there are common symptoms worth watching for:

• The device is sluggish or programs crash more than they used to.
• Strange pop-ups or browser redirects appear.
• Battery drains unusually fast on laptops or phones.
• Data usage spikes without a clear reason.
• Unknown apps or browser extensions you don’t remember installing.
• Files you can’t open, or a ransom note on screen (ransomware is not subtle).

How to Check a Device for Malware

If something feels off, work through the basics before jumping to worst-case conclusions:

• Run a full antivirus or EDR scan. Good security software can detect and remove most known threats.
• Review installed apps. Uninstall anything you don’t remember installing or don’t use.
• Open Task Manager (Windows) or Activity Monitor (macOS). Look for processes with weird names or unusually high CPU, memory, or network use.
• Audit your browser extensions. Remove any extension you don’t actively use or recognize. Extensions are a favorite hiding spot for malicious code.

What to Do If You’ve Been Hit

For a general malware infection:

1. Disconnect the device from the network (unplug ethernet, turn off Wi-Fi).
2. Run a full scan with your security software.
3. Quarantine or remove anything flagged.
4. Change your passwords from a different, clean device.

For a ransomware attack:

1. Disconnect immediately to stop encryption from spreading to shares and backups.
2. Don’t pay the ransom. Payment does not guarantee you get your files back, and it funds the next attack.
3. Report the incident to law enforcement. In the U.S., that includes the FBI’s IC3.
4. Restore from clean, offline backups. This is why backup strategy matters before anything goes wrong.
5. Bring in an experienced incident response team to find the root cause and close the hole. Otherwise you’ll just get reinfected.

How to Avoid Malware in the First Place

• Keep operating systems, browsers, and applications fully patched.
• Use modern endpoint protection with EDR, not just traditional antivirus.
• Train your team to spot phishing and social engineering attempts.
• Use strong, unique passwords plus multi-factor authentication on every account.
• Maintain frequent, tested, offline backups.
• Be skeptical of unexpected attachments, links, and USB drives.

Protect Yourself from Malware

Staying ahead of modern malware requires a mix of the right technology and the right habits. Traditional signature-based tools alone are not enough against polymorphic code, fileless attacks, and double-extortion ransomware. You need layered defenses, active monitoring, and a plan for when something slips through anyway.

If you need help hardening your environment or responding to an active incident, contact us. We’ll help you figure out what you’re up against and what to do about it.

About the Author

Brian Largent

Father to five, husband to one, founder, CEO, and all around swell fella (or so I'm told)