There are PC viruses that captures FTP login details while you are using them. They can then connect to your FTP account and change the files on your website, infecting it with malware.
If this has happened to you, take the following steps:
If you are still not certain if your site has been repaired, please raise a Support Ticket with the Customer Services team.
Article ID: 508
Created On: Tue, Mar 17, 2015 at 4:20 PM
Last Updated On: Thu, Apr 23, 2015 at 12:42 PM
Online URL: https://www.heartinternet.uk/support/article/what-do-i-do-when-my-site-is-infected-with-malware.html