We subscribe to a service which monitors attacks and removes any such threats. There was one last week with a delay - we had changed our FTP PW and the security service wasn't notified, so they couldn't remove the malicious code.
It's fixed and AFAIK, Trend is working from an old list. I just ran an AVG scan on it and it comes up clean.
http://www.avg.com.au/resources/web-page-scanner/
I will check again tomorrow and see if Trend has updated their list. It happens so fast I don't think they are running a scan, but simply checking a lookup table.