avast detect but not avast 5?

Viruses and worms
1

look at this virustotal link , why is it that avast detects it but not avast 5?

http://www.virustotal.com/file-scan/report.html?id=bc275f42deb7ffab9ef91b067503226f9996e0cf4c72769818ae0b2b03371927-1294577977

2

It is an old virus, so detetction for it may have been removed if it is not in the wild anymore…
also it can be a virus that only works on older OS not supported by avast 5

3

But it’s still detected by ESET and other these antiviruses.

4

The virus seems to be for DOS, this was the comment when i uploaded some samples to NORMAN

This file contains 5922 viruses (not Virut) for DOS (aprx 1988-1996). We detect 5730, the rest is various 1-st generation samples and so on. These things don't work anymore, but people still collect them. We won't prioritize these; if anything we might be removing the entire DOS catalogue from the defs.
http://forum.avast.com/index.php?topic=69579.msg584783#msg584783

but maybe somone from avast can step in and give some info…

5

Although it is called DOS:dream-2000, it doesn’t mean that windows can’t get the infection.
Keep in mind that Windows (up to Vista) is DOS based.
Windows 2000, Windows XP and later versions of Windows are NT based.

Anti-virus software should detect all in-the-wild malware.
Since it is not ITW anymore it doesn’t have to be detected.
Ofcourse it is prefered that it is being detected.

A possible explanation why it is not detected at the moment can also be that the detection caused a lot of false positives. In that case anti-virus programmers sometimes remove the detection till they have fixed it.

6

non-detecting prehistorical viruses in new versions is not a big problem imho… you would have to go to museum of viruses (does it even exist?) to meet such one and you would have to use DosBox to run/emulate it properly on your system… such old stuff is not a risk for the vast majority of currently used operating systems…

7

sorry.