A virus in computing is a malicious program that inserts itself into other programs or files and replicates when they run.
It can destroy data, slow devices down or give attackers access.
Definition of a Virus
A computer virus needs a host, such as a file or a boot area, and only becomes active when that host is run.
This distinguishes it from a worm, which spreads on its own.
Origin of the Term
Computer scientist Fred Cohen coined the term in 1983, based on biological viruses that use a host cell to reproduce.
Early examples spread via floppy disks.
Types of Computer Viruses
Viruses are distinguished by where they settle.
Boot Sector Viruses
They infect the start area of a storage medium and load during start-up before the operating system.
Direct Action Viruses
They become active when an infected file runs, infect further files and then terminate.
How Viruses Spread
A virus almost always reaches new devices through files.
Through Email and Instant Messaging
Infected attachments and links in emails or chat messages are the most common route.
They pose as an invoice, photo or document from someone you know.
Through Infected Websites and Downloaded Files
Manipulated downloads, fake updates and dubious software portals spread viruses.
Storage media such as USB sticks carry them further.
Impact of Viruses
The damage ranges from nuisance to serious losses.
Data Loss
Viruses can delete, damage or encrypt files.
Without a backup they are often lost.
Identity Theft
Some viruses download spyware that records passwords and banking details.
Criminals can then take over accounts.
Preventing Virus Infections
Prevention is easier than clean-up.
Use of Antivirus Software
Up-to-date protection software detects known viruses and suspicious behaviour before damage occurs.
Keeping System and Software Up to Date
Updates close holes through which viruses could enter without any user action.
Automatic updates should be switched on.
Dealing with Virus Infections
If an infection is suspected, calm and orderly action is important.
Isolating the Infected System
Disconnect the device from the network so the virus cannot spread further and no data leaks.
Using Antivirus Software
A full scan, ideally from a clean boot medium, finds and removes the malware.
Seeking Professional Help
For important data or company systems, experts should investigate the incident.
If in doubt, the system is rebuilt and restored from a clean backup.
Conclusion
Computer viruses are old but have not disappeared.
Current software, care with files and good backups protect reliably.