Author Topic: avast! Home Edition refuses to let me delete exclusions  (Read 19077 times)

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solcroft

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #15 on: May 17, 2007, 10:03:10 AM »
solcroft,

I do walk the talk. I have offered my system.  Tell me a web site to visit, I will provide you with an email address to send me an infected email.  I do not use P2P. 

Let me know how I might help you prove the point. 
Well, you could start by stopping the round-the-bush beating and try the steps I have outlined. Waiting to hear your results.

And oh, if autorun doesn't work on batch files for you, try writing a go-between vbs script between the inf and the bat. I'm not sure why, but autorun refused to launch the bat file on my system. Telling autorun to run a script than runs the batch file solves the problem for me though.

Offline alanrf

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #16 on: May 17, 2007, 10:07:41 AM »
Sorry I have not yet needed a USB key.  I transfer files across the network at home and only with trusted individuals across the net - and even then they are scanned as downloaded.

Is the USB key the only path you can come up with - I have offered other ways.

solcroft

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #17 on: May 17, 2007, 10:11:26 AM »
Sorry I have not yet needed a USB key.  I transfer files across the network at home and only with trusted individuals across the net - and even then they are scanned as downloaded.

Is the USB key the only path you can come up with - I have offered other ways.
I don't know of any malicious websites that serve malware with .ini filenames at the moment, and I'm not savvy enough to create one on the fly, unfortunately.

Still waiting for your results. Doesn't necessarily have to be a USB drive, that's just what commonly happens. ANY drive will do, including your HDD. I'm waiting.

Offline alanrf

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #18 on: May 17, 2007, 10:13:24 AM »
solcroft,

given the thought you have clearly put into this would you not suggest that any system user should not allow autorun and instead perform a thorough scan of a USB drive before using any data/executables on it?

Have you done this with your example of an infected USB drive?  Did it get past the avast scan?   

Offline igor

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #19 on: May 17, 2007, 10:15:11 AM »
I'm currently trying to completely wipe clean the exclusions list of the Standard Shield for testing purposes. However, the Standard Shield apparently refuses to let me do that - it re-adds some exclusions back to the list automatically every time I remove them all.

Is there some way to get around this problem? Thanks in advance.

Basically, the questions already contains the answer. Yes, avast! puts the default set of exclusion back when all the exclusions are removed. So, if you keep one exclusion at least (could be your own one, pointing to an non-existend folder maybe, it should be kept intact.

some Hupigon variants HAVE been using the .ini extension to camouflage themselves lately

Any more info on these?

Offline alanrf

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #20 on: May 17, 2007, 10:25:02 AM »
You and Igor appear to be in much closer time zones than I am to you (it is 1.20 am here in California).  I will leave you to chat with Igor and review the thread when I am around again and see what has transpired in the discussion. 

Maybe it is time I got a USB drive.

solcroft

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #21 on: May 17, 2007, 10:26:38 AM »
Basically, the questions already contains the answer. Yes, avast! puts the default set of exclusion back when all the exclusions are removed. So, if you keep one exclusion at least (could be your own one, pointing to an non-existend folder maybe, it should be kept intact.
Thanks for the tip, I'll try it out. Still, I think this is an issue that warrants attention; I'd never have realized avast! re-added the exclusions by itself if I hadn't renamed a few malware file extensions purely on a whim.

Any more info on these?
It depends on what you're after. They're just fairly standard Hupigon samples, with (I'd imagine) some tweaks to the code here and there, maybe an extra packer or two, and, of course, dropping fake .ini files (which were actually simply renamed executables) instead of .exe files as they used to do.

solcroft,

given the thought you have clearly put into this would you not suggest that any system user should not allow autorun and instead perform a thorough scan of a USB drive before using any data/executables on it?

Have you done this with your example of an infected USB drive?  Did it get past the avast scan?
That wasn't what I asked. You were the one who claimed never, and then threw out a challenge to me to prove you wrong. So go ahead. Try it. Walk the talk, like you claim you do. I'm waiting for your results.

Offline alanrf

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #22 on: May 17, 2007, 10:41:40 AM »
A final couple of thoughts before I sleep.

This is a two way street, neither of us jumps to the others commands.  I have made several offers to assist you to try to show me how the infection would get onto my system with avast up and running and where avast has the opportunity to scan the data being added to my system.  You seem to have ignored my questions about whether you are relying solely on the 'on access' scanner as the only protection in avast and my comment about P2P scans. 

Your point still appears to be that the infection must be deliberately introduced onto the system before avast can scan it. 

It may well be that, in scanning the conversation, Igor may tell you that you have found a way round the defenses of avast.  If he does then I need to perform no test.  On the other hand, if later today the issue is still under discussion I will go ahead and test with your deliberate infection suggestion. 

solcroft

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #23 on: May 17, 2007, 12:21:46 PM »
A final couple of thoughts before I sleep.

This is a two way street, neither of us jumps to the others commands.  I have made several offers to assist you to try to show me how the infection would get onto my system with avast up and running and where avast has the opportunity to scan the data being added to my system.  You seem to have ignored my questions about whether you are relying solely on the 'on access' scanner as the only protection in avast and my comment about P2P scans. 

Your point still appears to be that the infection must be deliberately introduced onto the system before avast can scan it. 

It may well be that, in scanning the conversation, Igor may tell you that you have found a way round the defenses of avast.  If he does then I need to perform no test.  On the other hand, if later today the issue is still under discussion I will go ahead and test with your deliberate infection suggestion. 
All I can say is, the one who's trying to weasel around now looks very suspiciously to be you. ;)

You claimed to be a man of action, yet for one who accused people of trying to weasel around you seem to be quite wordy and articulate now, and with precious little to be seen in terms of real action; none at all, in fact. So go ahead. Pretend that you believe the USB drive is malware-free, and stick it into your autorun-enabled computer, leaving avast! on all the time. Still waiting for your results here.

ReWritable

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #24 on: May 17, 2007, 04:25:37 PM »
Result is  : let's take a walk Solcroft. You outsit too long in front of monitor and radiation etched your nerve cells maybe a second head starting grow up.  (it could be serious u should do something with it)  :-[

Offline Vlk

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #25 on: May 17, 2007, 05:50:08 PM »
Hi solcroft,

thanks for reporting this - it's indeed an interesting issue. Well in fact two issues. The first being the inability to prune the default exception list (of which we were sort of aware) and the second, more serious, the one with the "start" command being able to launch a file with arbitrary extension. This is indeed an oversight on our part, and should be fixed.

We'll try to think of a viable solution for the next update.

Cheers
Vlk
If at first you don't succeed, then skydiving's not for you.

Offline alanrf

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #26 on: May 17, 2007, 11:48:11 PM »
Even though Vlk has noted the potential of this threat and the need for improved detection of it I thought I would still perform the test.

While I was drifting off to sleep it occurred to me that this threat must have existed since the year dot.

Before I proceed let me advise others reading through this ... don't do this at home.

Anyway ...

1) I turned off all avast protection.
2) I recovered from my store a piece of malware.
3) I renamed the malware to 1.ini (as requested by solcroft)
4) created the bat file to start 1.ini
5) placed the files on a USB drive
6) I turned back on avast protection

I could have gone to the trouble to make it autorun - I did not - I will return to it in a moment.

7) I started the bat file from the USB drive.

The result was the malware file (1.ini) was opened (without any warning from avast) and - on my system - was instantly displayed as a screenful of hex characters in my favorite text editor. 

After that I then made a "right click" on the USB drive and selected the avast scan from the context menu.  avast immediately produced its warning popup window and alarm reporting the infected 1.ini file.

Why did it not perform as solcroft expected?  I had to go lookup the start command to find out why.
 
To be fair to solcroft in most systems it probably would.  In my system I have associated .ini files with my favorite text editor since it recognizes the format of .ini files and gives me a nice color coded display of them.  However, anyone could avoid the specific .ini file issue by simply associating the .ini file with Notepad.exe.  The start command simply opens up the program specified for the filetype ... so as it says in the help file ...

start WORD.DOC

would open up the program associated with .DOC files.  In my case, for 1.ini, it opened my text editor.

The autorun issue. 

As I noted earlier in the thread this test required me to turn off avast protection in order to introduce the malware into my system.  As reported above, avast's quickscan picked up the infected 1.ini file.  solcroft did specify that the USB device should be autorun.  With this there would be no chance for the user to scan the device before it started executing whatever was on it. I believe that the malware filetype would have to be one that was considered innocuous by avast and not have a managing program associated with the filetype - solcroft may have done more research on other filetype exposure.

This exposure has existed since autorun came along - it could even have been done with a diskette (if the user did not bother to scan the diskette).  I am a little surprised that it has not been closed yet. 

This is not the first concern that has been raised with autorun and USB devices.  Were I running a home system where my children were inviting friends over and sharing information on USB devices I suspect I would not permit autorun on the system. 

I am glad to see the response from avast that they will be seeking a solution and I look forwarding to seeing it in the next release. 

In the meantime - the other avast shields, the Webshield, the P2P scanner and the Internet Mail scanner can all help prevent the malware getting into our systems in the first place - along with using quickscan.exe on all files downloaded.  Still best to be very wary about whose USB keychain devices you allow on your system.
« Last Edit: May 17, 2007, 11:49:48 PM by alanrf »

solcroft

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #27 on: May 18, 2007, 07:59:35 AM »
The result was the malware file (1.ini) was opened (without any warning from avast) and - on my system - was instantly displayed as a screenful of hex characters in my favorite text editor.
Interesting... but not very honest of you. The "start" command checks the content type of the file being launched, instead of its extension type. If you rename a real .exe file with a PE file header to .ini, .tmp or any other extension you care to think of, the "start" command will STILL launch it as an .exe file, instead of checking its associations as you claim it does.

Eagerly awaiting the next version of avast!.

Offline alanrf

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #28 on: May 18, 2007, 08:27:15 AM »
Sir,

at best you are unforgiving to question my honesty.  I will refrain from further description of your honor, though I will question your capacity in software testing.

I have just, from the start, repeated my tests that followed your requests to the letter.  The results are identical.

I see nothing in the documentation that says the start command checks the content type as priority.  I have reported precisely as my Windows XP fully up to date SP2 system has responded.
« Last Edit: May 18, 2007, 08:30:45 AM by alanrf »

solcroft

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Re: avast! Home Edition refuses to let me delete exclusions
« Reply #29 on: May 18, 2007, 08:52:48 AM »
I will refrain from further description of your honor, though I will question your capacity in software testing.
So will I, mine good sir, so will I. ;)

Would you mind sending the afore-mentioned file to me, by any chance?