File-infecting Virus: What it is, warning signs, and how to remove and prevent it

File-infecting Virus

What it is

A file-infecting virus hides inside legit programs (like .exe or .dll). When you run the program, the virus runs too - then copies itself into other executables, spreading across the PC and sometimes network drives or USBs.

What you may notice

  • Programs crash, won’t open, or act strangely

  • Executable files change size or reappear after deletion

  • Antivirus alerts keep coming back after a reboot

  • PC gets slower; fans spin up even when idle

How it spreads

  • Running an already-infected app or game mod

  • USB drives and shared folders with infected executables

  • Email attachments or downloads from sketchy sites

Clean it up (fast steps)

  1. Disconnect from the internet and unplug external/USB drives.

  2. Run a full anti-malware scan; quarantine what it finds and reboot.

  3. Rescan; if system files are damaged, repair or reinstall from clean media.

  4. Restore only from known-good backups made before the infection.

  5. Reconnect drives one at a time and scan them before use.

Prevent it

  • Install apps from official sources; avoid cracks and unknown “patchers.”

  • Keep Windows, browsers, and security tools updated.

  • Show file extensions so report.pdf.exe doesn’t fool you.

  • Scan USBs and disable autorun; be cautious with shared folders.

  • Use unique passwords + MFA to limit spread via accounts.

    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

      • Related Articles

      • Computer Virus

        What it is A computer virus is malware that copies itself into other files and programs—so every infected file can spread the infection again. That’s why outbreaks snowball. Viruses can slow your PC, break apps, or hide other threats. See our ...

      • Multipartite Virus

        What it is A multipartite virus is malware that attacks more than one place at once - for example the boot sector and your files. That dual foothold helps it spread faster and makes cleanups tricky, since removing one part can leave the other hiding. ...

      • Resident Virus

        What it is A resident virus is malware that loads part of itself into memory (RAM) and stays active after the original infected file has closed. Because its code hooks into system functions, it can silently infect other files as they are opened or ...

      • Virut

        What it is Virut is a Windows file-infecting virus that also turns your PC into part of a botnet. It slips its code into many EXE or SCR files and then connects to attacker-controlled IRC servers to get commands. It changes its look each time ...

      • Macro Virus

        What it is A macro virus hides inside Office files like Word documents or Excel spreadsheets and runs tiny programs called macros when you open the file. Criminals use it to download more malware or steal data. For background and safe settings, see ...