Just over a year ago I built a friend of a friend a website to advertise their rental apartment, no problems all went well and then a few months ago I was asked if they could have the files themselves to enable them to update it themselves. They know a little html and as I hadn't charged for the building of the site I said yes. I checked a couple of times, but nothing had been changed.
Last night I received an email to say that the website was blocked and that there was a trojan on it. I checked it out and this was the case, google was blocking it and had been for about a month. I tried to view the file through cuteftp but access was denied and AVG flagged a JS obfuscated trojan. On looking at the size of the index page, I did notice that it was much larger than that held on my computer. I deleted the page.
I'm still waiting to here whether they had uploaded a script onto the site and there was no JS on the site when I built it.
My friend asked whether it could have been hacked, but somehow I think unlikely as only the index page is affected although the whole site is blocked at the moment.
While waiting to here what they may have loaded onto the index page I wondered what sort of JS scripts would have caused this problem.

Rosalind