Avast! reports when visiting our site: Trojan horse was found... Please help

Viruses and worms
1

Hello,

last two days when wisiting our site/forum (it is SMF 1.1.8 forum), our users who are using Avast! are blocked, this it report:
Trojan horse was found: index.php{gzip} contains sample of ‘HTML:IFrame-CA [trj]’!
snapshot: http://i44.tinypic.com/2e1ht9i.jpg

We can’t find nothing suspicious (Iframes, wierd urls, etc) in index.php file. Do you have idea what is problem and how we can correct this?

2

You may have to contact your forum administrator for a site maintenance.

The forum page appears to be compressed.

3

Hi efzgforum,

See what you get scanning here: http://linkscanner.explabs.com/linkscanner/default.aspx

I get an all green from Exploit Prevention Lab LinkScanner and from Norton Safe Web,

polonus

4

Nothing from my scan. If it still does for you, try it from another computer with avast and let us know.

5

I have just visited the link in your image and no alert.

6

I visited your forum also and got no alert from avast.