•  Email as an attachment, using either harvested email accounts or collecting e-mail accounts from address books of infected systems. The actual sending of the e-mail can be achieved either by using existing mail server infrastructures or embedding the mail server in the payload of the malicious code.
       •  Sharing programs infected with a Trojan horse.
       •  Accessing Websites embedding malware.
       •  Remaining in the computer memory and causing itself to be embedded in every program that is executed.
       •  Infecting the boot sector of a computer’s hard disk so that the virus code is launched every time the computer is started.
       •  Actively searching for data or programs on a computer’s storage device that the virus code can embed itself in.
       •  Accessing shared resources such as shared file systems on file servers.
       •  Actively using network connections to propagate (computer worms).
See Also: Means of Infection; Virus; Worm.