Reliability in danger?

[Zekobe]

When I set a test virus on the desk top and  run a
complete virus scan, Avast cannot find anything.

But if I run the file  alone separately  then the virus is found.

Why is that?

This is rising a question of credibily of Avast.

WinXP Home

Any comments?

[FreewheelinFrank]

Do you have the test file in a zip archive and the system scan set not to check archives?

[Zekobe]

It is openly in a text file on the desk top. Another copy in a folder.

The text is the copy of F-secure pages:
http://www.f-secure.com/v-descs/badtrans.shtml
http://www.f-secure.com/v-descs/badtrs_b.shtml

Maybe because there is not a real virus or even a test virus.
Erratic action to my mind in any case.

On the other hand "eicar" test in the same places behaves in a correct way.

[FreewheelinFrank]

Maybe because there is not a real virus or even a test virus.

Quite.

Erratic action to my mind in any case.

The individual file scan may be a deeper scan, probably detecting some of the text from the virus mentioned on the web page as the virus itself. This is probably not best described as "erratic" behaviour, as the scanner is most likely behaving as intended. Try a "thorough" complete scan and you may see the same detection.