What is a worm?
Like a virus, a worm is self-replicating malware. Unlike a virus, a worm is a standalone program and does not need to be part of another program to function. See also virus.
How does a worm work?
Some worms are only created to replicate themselves and not do harm, though they all at least consume some bandwidth and disk space. More malicious worms carry “payloads,” which can destroy files, install backdoors, encrypt files, and install malware.
Worms are often spread through spam attachments. They can be protected against by not opening untrusted email attachments, keeping your device’s operating system and programs up to date, and installing up-to-date antivirus software.