Hello!
Let us learn on worms that are malware in systems.
Worms :
Computer worm is a type of malware that can spread from one computer to another.
Worms moves through network of computers to search for weakness to infect and slow down the network.
Worms are often spread by email attachments that may seem safe but will be much dangerous.
They can also spread by software downloads and infected websites.
Once a computer is infected the worm send itself to the person's contact, using the email account and spreading to more computers.