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Diversified Tech Solutions Diversified Tech Solutions Technology · Security · Compliance

What Is Malware?

Definition

Malware (malicious software) is any program or code that is deliberately placed on a computer, phone, server, or website to cause harm: stealing data, spying, locking files, or giving an attacker control. NIST's glossary defines it as hardware, firmware, or software "intentionally included or inserted in a system for a harmful purpose."

How It Works

Malware is an umbrella term. NIST SP 800-83 Rev. 1, NIST's guide to malware incident prevention and handling, describes it as a program covertly inserted into another program to destroy data, run destructive or intrusive programs, or otherwise compromise confidentiality, integrity, or availability. Common families include:

  • Loaders and trojans that look harmless and fetch other malware.
  • Infostealers that harvest saved passwords and browser sessions.
  • Ransomware that encrypts files for extortion.
  • Botnet agents that let a criminal control many machines at once.
  • Website malware, such as PHP backdoors, webshells, injected JavaScript, and spam scripts on WordPress sites.

The usual delivery routes are email attachments and links, fake software updates, pirated or "nulled" software, and unpatched vulnerabilities. Once installed, malware often tries to persist (survive reboots and cleanups) and to call home to a command and control server for instructions. One infection is frequently a doorway for the next: the first program's job is often just to install another.

Real-World Example

In August 2023, the Justice Department announced a multinational operation that disrupted the Qakbot botnet. According to DOJ, Qakbot primarily infected computers through spam emails with malicious attachments or links, then delivered additional malware, including ransomware. It was used as an initial infection route by ransomware groups including Conti, REvil, and Black Basta. The FBI identified more than 700,000 infected computers worldwide, over 200,000 of them in the United States, redirected the botnet's traffic, and pushed an uninstaller to infected machines. DOJ also seized about $8.6 million in cryptocurrency.

Why It Matters for a Small Business

The FBI's 2025 IC3 report lists 893 malware complaints with $19,370,572 in reported losses. Those figures count only complaints filed under the malware crime type; ransomware, data breach, and business email compromise each have their own categories in the same report. Qakbot shows the pattern: one email attachment on one laptop can be the first step toward a ransomware attack. NIST notes that malware is "the most common external threat to most hosts." DOJ said Qakbot alone caused hundreds of millions of dollars in damage worldwide.

How to Spot It / How DTS Handles It

Signs: security tools disabled or alerting; unknown programs, scheduled tasks, or browser extensions; new admin accounts; unusual outbound traffic; and on websites, a Google or browser warning, or files that reappear after deletion.

DTS isolates the device or site, preserves evidence, identifies the malware family, removes every persistence point, and checks for stolen credentials. See our hacked WordPress cleanup service, or our malware warning guide.

Related Terms

  • Ransomware: the most damaging payload malware often delivers.
  • Backdoor: the persistence that lets malware come back.
  • Webshell: malware that lives on a web server.
  • Infostealer: malware that harvests saved passwords and sessions.
  • Botnet: networks of infected machines like Qakbot.
  • EDR: endpoint tools that detect malware behavior.
  • Malware scanning: how infections are found on sites and servers.

Sources

  • NIST CSRC Glossary, malware: https://csrc.nist.gov/glossary/term/malware
  • NIST, SP 800-83 Rev. 1, Guide to Malware Incident Prevention and Handling for Desktops and Laptops (July 2013): https://csrc.nist.gov/pubs/sp/800/83/r1/final
  • U.S. Department of Justice, Qakbot Malware Disrupted in International Cyber Takedown (August 29, 2023): https://www.justice.gov/opa/pr/qakbot-malware-disrupted-international-cyber-takedown
  • FBI Internet Crime Complaint Center, 2025 IC3 Annual Report: https://www.ic3.gov/AnnualReport/Reports/2025_IC3Report.pdf

Last updated October 14, 2026.