On the site change.org it's possible to start a petition.
We do not monitor, verify, or perform any background check on campaign starters, petition signers, or other users of Change.org.
Fraud prevention: We may use and disclose the information we collect from and about our users as we believe necessary to investigate, prevent, or respond to suspected illegal or fraudulent activity or to protect the safety, privacy, rights, or property of us, our users, or others.
They also state, that they store the IP address of users who have signed a petition:
An IP Address may be identified and logged automatically in our server log files whenever you use our platform and services, along with the time of your visit and the specific page(s) that you visited.
From what I could gather it would be very easy to create petitions with fake users to bring attention to a petition (or to reach a certain amount).
My question is simply:
How does the site ensure that there's no voter fraud?