How can you protect yourself from malicious code on removable media?

Scan every USB drive, external hard drive, or other removable device with up-to-date antivirus before opening any files on it. Never plug in media you found or received from an untrusted source, since attackers deliberately plant infected drives.

What are examples of malicious code?

Common examples include viruses, worms, Trojan horses, ransomware, spyware, adware, rootkits, and malicious macros or scripts embedded in documents. They differ in how they spread and what they do, but all are written to damage systems or steal information.

How does antivirus software prevent viruses?

Antivirus scans files against a database of known malware signatures and watches for suspicious behavior, then quarantines or removes threats. It only catches what its current definitions recognize, so keeping it updated and scanning files before opening them are essential.

What should you do before opening an email attachment?

Confirm the sender is known and the attachment is expected, be wary of urgent or too-good-to-be-true messages, and scan the attachment with up-to-date antivirus before opening it. If anything seems suspicious, do not open it and delete the email.

How can you prevent viruses and malicious code?

Q: What is malicious code?

Malicious code is any software designed to harm a system or gain unauthorized access, including viruses, worms, Trojan horses, ransomware, spyware, and malicious scripts or macros. It can corrupt files, steal data, encrypt files for ransom, or spy on activity, usually after a user unknowingly runs it.

The answer

You prevent viruses and malicious code by combining several defensive habits rather than relying on any single one. The most effective actions are: scan all email attachments and external files or removable media before opening them, avoid clicking unknown or suspicious links and pop-ups, keep your operating system and antivirus software updated, and download only from trusted, verified sources. Each habit closes off one of the main pathways attackers use, and together they form layered protection.

What malicious code actually does

"Malicious code" is any software written to damage or gain unauthorized access to a system. It includes viruses, worms, Trojan horses, ransomware, spyware, and malicious scripts or macros. Once it runs, it can corrupt or delete files, steal passwords and personal data, encrypt your files for ransom, spy on your activity, or turn your device into part of a botnet. Crucially, most malicious code needs you to trigger it — by opening an infected attachment, running a downloaded file, plugging in an infected USB drive, or clicking a booby-trapped link. That is why prevention focuses on controlling those entry points.

Layered prevention

Good defense addresses each common infection vector:

Email: Do not open attachments or click links from unknown or unexpected senders. Scan every attachment with antivirus before opening it, and be suspicious of urgent or too-good-to-be-true messages, which are classic phishing lures.
Removable media: Scan USB drives, external hard drives, and other removable media with antivirus before opening any files. Never plug in a device you found or received from an untrusted source — attackers deliberately leave infected drives to be picked up.
Downloads and websites: Only download software from official or trusted sources. Avoid clicking pop-ups and "you've won" ads, and be wary of free software bundled with extras.
Updates: Keep your operating system, browser, and applications patched, and keep antivirus/anti-malware definitions current. Updates fix the security holes malware exploits.
Backups and least privilege: Back up important data regularly so ransomware cannot hold you hostage, and avoid using an administrator account for everyday tasks.

How antivirus fits in

Antivirus software scans files against a database of known malware signatures and watches for suspicious behavior, quarantining or removing threats it finds. But it is only as good as its last update — new malware appears constantly, so outdated antivirus misses recent threats. That is why "keep antivirus updated" and "scan before opening" go hand in hand: the tool provides the detection, and your habit of scanning gives it the chance to catch something before it runs.

The bigger picture

No single step is enough on its own. A fully patched machine can still be infected by a user who runs an unknown attachment, and cautious habits can still fail against a brand-new exploit if software is unpatched. Prevention works because it is layered — scanning, cautious clicking, trusted downloads, and constant updates each catch what the others might miss. Practicing all of them together is how you reliably keep viruses and malicious code off your system.