Malicious Code - What it is, warning signs, and how to prevent it

Malicious Code

What it is

Malicious code is any program or script written to harm systems or data. It exploits weaknesses to steal information, corrupt files, spy on activity, or open a backdoor so attackers can get back in later. Think of it as code with the goal of breaking trust rather than doing useful work.

Why it matters

A single run of malicious code can lead to account theft, data leaks, downtime, and costly recovery. Because it often hides inside normal-looking files or websites, prevention and quick detection are key.

How it works - quick tour

  • Exploits software bugs to run without permission

  • Drops payloads like spyware, ransomware, or cryptominers

  • Persists using startup entries, scheduled tasks, or services

  • Phones home to command servers to fetch new instructions

What you may notice

  • Sudden pop-ups, redirects, or tool crashes

  • New processes or startup items you did not add

  • High CPU or network use when idle

  • Security tools disabled or failing to update

Prevent it

  • Update OS, browsers, and apps quickly

  • Install software only from official sources

  • Turn on EDR or reputable anti-malware with real-time protection

  • Use MFA and a password manager to limit damage

  • Block risky sites with DNS or web filtering

    Glossary (A–Z)

    All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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