| A worm is a computer program that copies and multiplies itself by using computer networks and security flaws. | A virus is a malicious program which has the ability to execute and replicate itself. |
| A worm is self-sufficient i.e., it has the ability to spread itself without the use of another program or a user. | A virus attaches itself to other programs and spreads across the computer system. |
| Worms do not affect functioning of the system but interrupts services and drastically decrease the available memory of the system. | Once loaded, viruses start damaging the system by modifying information. |