It could be a false positive and could be cleared on the next major update. I would suggest running Dr.Web Cureit (free version) from here. Things to know; although it's free it has to be downloaded every time to have the most up-to-date version, so download and select 'run'. It will ask for a name and email and basic info such as gender, age etc. Some spam to look foreward to but nothing is for nothing really. Once started it goes to enhanced protection mode, meaning the desktop will be greyed out during the scan. Your security programs will still be running in the background. It defaults to express scan but will still take some time depending on what you have on your HDD. After initial scan you can select a full scan but I wouldn't bother with that. Sometimes after the scan it will show if the hosts files have been changed. Don't bother using the program to set to defaults as you'll need to go to Microsoft to do that. One other thing is while scanning you'll get a single nag screen to purchase or trial the security suit. Click on the 'x'and it disappears. It's a good tool to use and can also be used from a usb drive if saved. If nothing found via Cureit then it looks more likely it's a false positive. Keep quarantining it in Avira until you get some updates to see if it clears.
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