Author Topic: Unable to scan: Exception in polymorph viruses code  (Read 5116 times)

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Hapax

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Unable to scan: Exception in polymorph viruses code
« on: January 03, 2007, 09:00:16 PM »
Hi

After installing avast, the result of every manual scan I do is that a large number of files cannot be scanned, the error message being:

Unable to scan: Exception in polymorph viruses code


The files in question are almost certainly not infected (other scanners don't find anything).
The total number of those error varies, if I make a full scan, it's in the range of 10k to 20k errors.
I reinstalled avast, but it didnt change anything.
One more thing: scanning one of the files, that threw such an error, with the Explorer extension does _not_ throw this error.


I'm using avast 4.7.892, with the latest definitions, running on an IBM T43 notebook with Windows XP Professional SP 2 (v.2096), Pentium M 1.73 GHz, 256 MB RAM.


I've seen a similar problem reported before on this forum, but apart from "re-install avast" (which I did), no other suggestions were made.
Anyone can help?

Offline Lisandro

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #1 on: January 03, 2007, 09:13:32 PM »
Unable to scan: Exception in polymorph viruses code
This is an old known error message that means very little for us users...
What I can say is that you don't have to worry that much. The files are most probably clean but avast can't scan them.
If you remove the 'hard errors' files from the report you won't see these files again.
I don't know other solution... maybe anybody from Alwil could help here...
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Hapax

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #2 on: January 03, 2007, 09:31:31 PM »
Thanks for the immediate answer, Tech.

What I can say is that you don't have to worry that much. The files are most probably clean but avast can't scan them.

If avast in fact does not scan those files, then having up to 30000 files on my computer not scanned when I do a full scan is actually worrying me a lot.


Offline Lisandro

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #3 on: January 03, 2007, 09:43:22 PM »
If avast in fact does not scan those files, then having up to 30000 files on my computer not scanned when I do a full scan is actually worrying me a lot.
Strange number of files...
Any info about the path and the extension of these files?
Maybe your avast installation is corrupted... but I'm not sure. Did you have any other antivirus in this computer in the past?
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Hapax

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #4 on: January 03, 2007, 09:53:43 PM »
If avast in fact does not scan those files, then having up to 30000 files on my computer not scanned when I do a full scan is actually worrying me a lot.
Strange number of files...
Any info about the path and the extension of these files?
Maybe your avast installation is corrupted... but I'm not sure. Did you have any other antivirus in this computer in the past?

It's basically almost all of my files on C: that aren't scanned (or that look they aren't scanned).
No pattern, as far as I can see, of which file types are and which are not scanned.

To my knowledge, my machine has been virus free for quite a while. I did reinstall the OS however a month ago, which is why I also needed to reinstall avast. Before that, I did not get the errors. As I said, I'm using Win XP SP2 now, before that I had XP SP1 installed.

Hapax

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #5 on: January 03, 2007, 09:58:47 PM »
If avast in fact does not scan those files, then having up to 30000 files on my computer not scanned when I do a full scan is actually worrying me a lot.
Strange number of files...
Any info about the path and the extension of these files?
Maybe your avast installation is corrupted... but I'm not sure. Did you have any other antivirus in this computer in the past?

sorry, just realized you asked about "antivirus" :)

yes, I also have AVG Anti-Spyware, Ad-Aware and Spybot installed, but only avast is set to be the resident protection.
Then again, I can't guarantee that none of the other programs have some of their processes running while I scan with avast.

Offline Lisandro

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #6 on: January 03, 2007, 10:02:40 PM »
I also have AVG Anti-Spyware, Ad-Aware and Spybot installed
These programs are avast-compatible.

Then again, I can't guarantee that none of the other programs have some of their processes running while I scan with avast.
Can you schedule a boot-time scanning?

Click on the Menu button.
Choose Schedule Boot Time Scan.
Doing so displays a dialog allowing you to schedule virus scanning.
Check Archives, if you want scan all the archives.
Specify whether all the disks or just a specific folder should be scanned.
Select Advanced options for scheduling details.
Select how to automatically process infected files.
Choose how to automatically process infected system files.
Click the Schedule button to confirm the settings.

Since avast! version 4.7.807 the for archive scanning at boot time has been considerably improved.
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Hapax

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #7 on: January 03, 2007, 10:58:54 PM »
Okay, now I'm worried:

I scheduled a boot time scan, which ran without stating an error message (that means that both boot time scan and scan initiated via Explorer extension don"t throw the error. Is there anything that those two functions have in common, which the manual scan does not share with them?). Just an idea: Maybe both of them simply don't throw the same error messages as the manual scan.

Then, following Tech's question about other anti virus programs, I ran a manual avast scan in safe mode, where services of other av programs shouldn't interfere, but the "Unable to scan" error occurs in safe mode, too.

Now, just to see if I'm actually protected at all, I downloaded the EICAR test file, but when I scan it with avast, no matter how, nothing happens:
executing eicar.com doesn't trigger the avast on-access scanner (which is running),
an Explorer extension scan claims the file is not infected,
manually scanning the folder in which the file is located yields the known "Unable to scan" error.

Isn't avast supposed to report the eicar test file "virus"?
I guess that answers the question whether I can safely ignore the "unable to scan" error...

Offline Lisandro

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #8 on: January 03, 2007, 11:07:57 PM »
I scheduled a boot time scan, which ran without stating an error message (that means that both boot time scan and scan initiated via Explorer extension don"t throw the error. Is there anything that those two functions have in common, which the manual scan does not share with them?). Just an idea: Maybe both of them simply don't throw the same error messages as the manual scan.
The standard scanning should be as the same as boot time one, or even deeper. So, maybe the messages aren't that strange.

"Unable to scan" error occurs in safe mode, too.
The problem isn't on the Safe Mode or services, but on avast unpacking capabilities and the files themselves.
Please, post some of their names and paths...

Now, just to see if I'm actually protected at all, I downloaded the EICAR test file, but when I scan it with avast, no matter how, nothing happens:
executing eicar.com doesn't trigger the avast on-access scanner (which is running),
Your avast installation is corrupted... Which is your Standard Shield sensibility? High or Normal?
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Offline Vlk

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #9 on: January 03, 2007, 11:09:54 PM »
This is a known compatibility issue between avast and BETA versions of XP SP2.
Is there a specific reason why you're using a pre-release version of SP2 (you said you had build 2096) and not the official one (build 2600)?

The thing is, the beta had some bugs that were fixed in the official version but avast can't cope with them...

Thanks
Vlk
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Hapax

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #10 on: January 03, 2007, 11:29:09 PM »
Is there a specific reason why you're using a pre-release version of SP2 (you said you had build 2096) and not the official one (build 2600)?

Now that I know it kills avast, not anymore :)

Thanks alot for your help, Tech, Vlk!

Offline Lisandro

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Re: Unable to scan: Exception in polymorph viruses code
« Reply #11 on: January 04, 2007, 12:54:20 AM »
Sorry  :'(
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