Strange case !

[cvsa]

A friend of mine, avast! user, received a mail with 2 attached  files.
The sender told her that she has sent only one attached file

the second file was something like 07-xx.gif

Avast and jotti's  scan didn't find any virus in it but, opening thefile (i know it's not very smart) , my friend had the surprise to see scrolling pictures of her children (that were probably on her computer) with ads picture in between 

did you ear of such a thing (the file has been sent to alwil) and put in the chest......??

[DavidR]

Whilst they may have only attached one file, if they included an image embedded in the email, that may be the second attachment. Or the sender is using an email program that has additional functionality and a little Ad Icon from the company.

No matter how many attachments there are with the email I believe that avast scans them all.

[cvsa]

but my main question is : can a .gif file contain a virus/adware ?

[DavidR]

Ahh but you didn't mention that, currently .gif files are safe, that may not remain the case in the future.
As has happened with .jpg images they too used to be thought of as safe but can be manipulated for malicious purposes (jpeg expliot).

But avast detects jpg exploit, check to see:
http://www.nod32.de/download/jpegcompoc.jpg
http://www.nod32.de/download/jpegcompoc.zip