Worms

A worm is a type of malware that causes unexpected or damaging behaviour on an infected computer system. What sets it apart from a virus is not what it does, but how it operates and spreads.

The central difference is that a worm does not need a host program or software to insert its code into. A virus attaches itself to an existing file or program, but a worm is a standalone program that works on its own. It does not hide inside something else; it is a complete, independent piece of software.

The second major difference lies in how each replicates. A virus needs human triggering — it only spreads when a user opens or executes the infected file. A worm, by contrast, replicates on its own, with no human action required, and can spread to other computers through the network automatically.