If you need to stop a scan that's currently running there are two options:
Option 1:
Log in to your account.
Click on the Scans In Progress timer in the top right navigation menu.
Click the X icon.
Click Ok to confirm.
Option 2:
Log in to your dashboard.
Select Targets in the left navigation bar.
Select the Scanning section towards the top of the page.
Click the X icon to the right of the time remaining.
Click Ok to confirm.