- Electronic mail or instant messengers — Worm copies itself as an attachment.
- File sharing — Creates a copy of itself or infects a file as a virus on removable media.
- Remote execution capability — Worm executes a copy of itself on another system.
- Remote file access or transfer capability — Worm uses a remote file access or transfer service to copy itself from one system to the other.
- Remote login capability — Worm logs onto a remote system as a user and then uses commands to copy itself from one system to another.
