This is called an 'infection vector'. In a similar way, computer viruses need to be shifted from one place to another by users, accidentally or not.

Science Creating undetectable computer virus 'surprisingly simple' Andre Mayer · CBC News · Posted: May 30, 2012 12:39 PM PDT | Last Updated: May 30, 2012 ...

Although the virus didn't cause serious damage, it displayed the phone number of the brothers' computer shop for repairs. 'It was some dumb little practical joke.' ...