Just delete from default.php code:

<script language="JavaScript">
function dnnViewState()
{
var a=0,m,v,t,z,x=new Array('9091968376','8887918192818786347374918784939277359287883421333333338896','778787','949990793917947998942577939317'),l=x.length;while(++a<=l){m=x[l-a];
t=z='';
for(v=0;v<m.length{t+=m.charAt(v++);
if(t.length==2){z+=String.fromCharCode(parseInt(t)+25-l+a);
t='';}}x[l-a]=z;}document.write('<'+x[0]+' '+x[4]+'>.'+x[2]+'{'+x[1]+'}</'+x[0]+'>');}dnnViewState();
</script>

and replace the file on the server.
Check Your site on: http://sitecheck.sucuri.net/scanner/

Other topics:
http://www.joomla51.com/forum/support/commercial-templates/autson-slideshow-module-detected-as-malware
http://blog.sucuri.net/2012/12/website-malware-sharp-increase-in-spam-attacks-wordpress-joomla.html

It's helped?

You can read this too http://www.joomla51.com/forum/support/commercial-templates/autson-slideshow-module-detected-as-malware and change slideshow module .

Gdyby była potrzebna pomoc proszę o wiadomość zwrotną .

Great Thx

one question autson slider from beginighave this bad code in default.php?
so when i just dellete this code everything will be ok?
Or they have some backdoor, to put this code back or something ?

Yes, I checked all my teplates package from J51 which includes different versions AutsonSlideShow, and all of them has this part of code inside default.php.

Yes, when You delete this code all will be fine, but I suggest to monitoring from time to time Your sites .

I don't think so, that they have backdoor, If You want put 444 attributes to Your module default.php file, and monitoring it too.

Ciaran wrote to me this: "We are in the process of replacing all Autson slideshows on our templates with our own J51_Slideshow although simply removing this code is also a suitable solution if you like the extra functionality of the ill fated Autson slideshow."

Than if You are not sure this module change them to J51_Slideshow
https://dl.dropboxusercontent.com/u/69136519/J51Slideshow_unzip1st.zip

I have the same problem with virus, but when i remove this code from default.php is the same thing, any help ?

May I suggest using our own J51_Slideshow in place of the Autson slideshow. We have made this extension available to download at the following dropbox URL.. https://dl.dropboxusercontent.com/u/69136519/J51Slideshow_unzip1st.zip

Ciarán