Anti-virus software

Anti-virus software, also called anti-malware software, monitors a device for malicious software and attempts to block infection.

What it checks

It scans files, programs, incoming emails and removable storage such as a USB stick. It can also check a link when you click it in a web page or email, before the page opens.

To judge whether something is dangerous, the software compares the suspicious file or its behaviour with a database of known malware signatures, often called the definitions. A signature is a pattern that identifies malware which has already been studied. For example, if you download a game mod from an unfamiliar website, the scanner may find that its code matches a known harmful program.

Handling a threat

If an infected or suspicious file is found, the software can remove, delete or quarantine it. Quarantining means moving the file to an isolated place where it cannot run or spread, while keeping it for checking. This protects your data and stops malware reaching other files or devices.

The software also alerts the user. That warning lets you cancel a download, avoid opening an attachment or close a page, and then decide how to respond.

Keeping it effective

Anti-virus software must be kept up to date, often by turning on automatic updates. New malware appears all the time, so an old database will not recognise the latest threats.

Anti-virus software and a firewall do different jobs. Anti-virus software scans files and looks for malware; a firewall filters network traffic. A firewall will not remove malware, and anti-virus software does not filter network traffic.