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Posible Combofix False Positive


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#1 akwe-xavante

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Posted 10 January 2012 - 01:45 PM

Combofix False Positive - Avira's Strange behaviour

On downloading Combofix from: http://www.bleepingcomputer.com/download/anti-virus/combofix

Avira flashed up the following:

Virus or unwanted program 'RKIT/Agent.4368790 [trojan]'
detected in file '\\10.1.1.20\Devil's Backbone\MyTools\ComboFix\ComboFix.exe.
Action performed: Deny access

Knowing that it is safe anyway i continued to download, avira's free version cannot delete from a mapped drive anyway.

On copying the downloaded file to the desktop and right clicking and selecting "Scan selected file with Avria" Avira completes the scan and finds nothing!

Downloading the file a second time from bleepingcomputer.com, avira does not flash up the warning again!

Avira flashes up another message when copying the downloaded file to a USB Memory stick!

This time:

Virus or unwanted program 'RKIT/Agent.4370492 [trojan]'
detected in file 'J:\MyTools\ComboFix\ComboFix.exe.
Action performed: Deny access

I think it is denying access to the file being overwritten rather than the file that i have just downloaded but the file being overwritten was also downloaded from bleepingcomputer.com on Friday 6th January 2012 (4 Days ago). Avira didn't detect anything wrong on Friday when Combofix was downloaded and used. Combofix appeared to run and do its job as normal, nothing unusual happened at the time or since Friday!

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#2 cryptodan

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Posted 10 January 2012 - 02:17 PM

No one should be using ComboFix unless specifically instructed to do so by a Malware Removal Expert who can interpret the logs. It is a powerful tool intended by its creator to be "used under the guidance and supervision of an expert. Using this tool incorrectly could lead to disastrous problems with your operating system such as preventing it from ever starting again. When issues arise with new malware infections or other security tools conflicting with ComboFix, experts are aware of them and can advise users what should or should not be done while providing assistance. Those attempting to use ComboFix on their own do not have such information and are at risk when running the tool in an unsupervised environment. Please read the pinned topic ComboFix usage, Questions, Help? - Look here.

What specific issues are you having that requires using ComboFix?

Compliments of QuietMan7

Please follow the instructions in ==>Malware Removal and Log Section Preparation Guide<==.

Once the proper logs are created, then make a NEW TOPIC and post it ==>HERE<== Please include the link to this topic in your new topic and a description of your computer issues and what you have done to resolve them.

If you can produce at least some of the logs, then please create the new topic and explain what happens when you try to create the log(s) that you couldn't get. If you cannot produce any of the logs, then still post the topic and explain that you followed the Prep. Guide, were unable to create the logs, and describe what happens when you try to create the logs.

Once you have created the new topic, please reply back here with a link to the new topic.

Most importantly please be patient till you get a reply to your topic.

Edited by cryptodan, 10 January 2012 - 02:17 PM.


#3 akwe-xavante

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Posted 10 January 2012 - 02:26 PM

Thank you Bleeping Madman for your reply.

Combofix downloaded on friday was used for removing a Virus on a different computer later on in the day, virus was removed and the computer is now clean, problem resolved.

However your reply doesn't in any way help with my original post.

The infected computer wasn't the computer being used to download Combofix.

4 days after downloading Combofix from bleepingcomputer.com Avira AntiVirus flashed a message up saying it contained malware.

Edited by akwe-xavante, 10 January 2012 - 02:37 PM.


#4 cryptodan

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Posted 10 January 2012 - 03:05 PM

My reply is for you to have the log analyzed and to make sure your computer is cleaned up. Also Combofix should not be used without supervision from a malware removal specialist. Running it without supervision and on your own accord can have disastrous effects.

#5 akwe-xavante

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Posted 10 January 2012 - 03:16 PM

Hello Bleeping Madman or do i call you cryptodan,

Thank you again.

I have been using Combofix for years and i am very well experienced at virus and malware removal as well as repairing crippled computers afterwards etc

I don't require any help using combofix at this time.

My concern is that i downloaded combofix from bleepingcomputer.com on friday 6th jan 2012 and today Avira Antivus claimed that that download contained a rootkit.

Todays download is rootkit free!

Fridays download was overwritten by todays download unfortunatly.

#6 cryptodan

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Posted 10 January 2012 - 03:20 PM

Posting the log for analysis will better assist us in assisting you and the developer.

#7 akwe-xavante

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Posted 10 January 2012 - 03:28 PM

Where am i failing to get my reason for posting on this forum across to you!?

Fridays download was used to cleanse a computer of the virus infection it had, combofix was successful, the infected computer is now clean and virus and malware free.

The infected computer IS NOT the computer that is being used to download Combofix from bleepingcomputer.com

Now OK a have had a thought......... Which log are you asking for? Avira's log or Combofix's log.

Avira is claiming that combofix (Downloaded on Friday the 6th January 2012) is infected with:

Virus or unwanted program 'RKIT/Agent.4368790 [trojan]'
detected in file '\\10.1.1.20\Devil's Backbone\MyTools\ComboFix\ComboFix.exe.
Action performed: Deny access

The info above is all the information there is in Avira's log file.

#8 cryptodan

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Posted 10 January 2012 - 03:34 PM

Combofix's Log not Aviras.

#9 akwe-xavante

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Posted 10 January 2012 - 03:42 PM

Unfortunatly Combofix's log is no longer available to me to post here.

Question: How on earth will Combofix's logfile after successfully completing a scan and removing a number of viruses and malware on a completely different computer (Computer A) help you to figure out why Avira on (computer B ) is claiming that fridays download from bleepingcomputer.com is infected with a rootkit?

Combofix was downloaded from bleepingcomputer.com and not from any other website including combofix.org etc etc etc.

Computer B's operating system is SuSE linux 11.2 and not an M$ OS so it is not possible to run combofix on the computer that is being used to download it.

Edited by akwe-xavante, 10 January 2012 - 03:45 PM.


#10 akwe-xavante

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Posted 10 January 2012 - 03:56 PM

Having checked my browsers download history i can confirm that Combofix was download from bleepingcomputer.com at 07.40hrs on Friday the 6th January 2012.

Today Tuesday 10th January, several days later, Avira claims that the download contains a rootkit.

Todays download however is clean.

I think Fridays download was / is clean too. I believe this is a false positive.

#11 akwe-xavante

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Posted 10 January 2012 - 04:01 PM

Hello,

I now have an answer from an Avira Moderator who says:

Avira ist not detecting Combofix at this moment

Combofix 12.01.10.02
MD5
A1B142D98F844DD1076DDA2F19DFC4A1

I have to agree, because it isn't, todays download is clean according to my Avira install and according to an Avira Mod.

#12 akwe-xavante

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Posted 10 January 2012 - 04:11 PM

Hello and thank you once again,

Thank you for your help but at this moment in time i'm happy to just drop this thread and forget all about it.

It never happened.

I will as always continue to use Combofix, its an excellent product and a VERY BIG THANK YOU to the application developer.

An outstanding removal tool.

#13 cryptodan

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Posted 10 January 2012 - 04:19 PM

It shouldn't be used by anyone but those trained in malware removal. It can brick a computer to the point where the only way to restore it is a complete reinstall of the OS.

#14 akwe-xavante

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Posted 10 January 2012 - 04:25 PM

I am trained and with over 18 years experience in removing viruses, rogueware, swearware, rootkits and malware, repairing broken operating systems, pc hardware repairs and advanced data recovery from dead drives.

#15 quietman7

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Posted 10 January 2012 - 06:14 PM

Hello akwe-xavante

Please understand that cryptodan is simply responding in accordance with sUBs' (the developer) warning which says ComboFix is permitted for non-commerical purposes only and should not be used in an unsupervised environment. sUBs includes such a statement in his disclaimer which you see when running his tool.

It's not that ComboFix is dangerous, but that it is a powerful and complex tool. Using this tool incorrectly even by experienced techs could lead to disastrous problems with your operating system such as preventing it from ever starting again. Further, when issues arise due to complex malware infections, possible false detections, problems running ComboFix (i.e. stalling, hanging, crashing) or with other security tools causing conflicts, our experts are usually aware of them and can advise what should or should not be done while providing individual assistance. When false detections are identified, experts have access to the developer and can report them so he can investigate, confirm and make corrections. Those attempting to use ComboFix on their own do not have such information and are at risk when running the tool in an unsupervised environment.

We are only attempting to look out for the best interests of all our members (including you) when we provide these warnings. Our forums are targeted more for the novice user which makes up most of our membership. We provide help based on that premise since it is impossible for us to know the extent of a member's background, knowledge level and experience until we get to know them. I hope you can appreciate and understand why we do this.

With that said, let me explain what you most likely encountered.

Certain embedded files that are part of legitimate programs or specialized fix tools such as Combofix may at times be detected by some anti-virus and anti-malware scanners as a "Risk Tool", "Hacking Tool", "Potentially Unwanted Program", or even "Malware" (virus/trojan) when that is not the case. This occurs for a variety of reasons to include the tool's compiler, the files it uses, whether files are compressed or packed, what behavior it performs, any registry strings it may contain and the type of security engine that was used during the scan. Other legitimate files which may be obfuscated, encrypted or password protected in order to conceal itself so they do not allow access for scanning but often trigger alerts by anti-virus software.

Such programs have legitimate uses in contexts where a Malware Removal Expert asked you to use the tool or when an authorized user/administrator has knowingly installed it. When flagged by an anti-virus or security scanner, it's because the program includes features, behavior or files that appear suspicious or which can potentially be used for malicious purposes. Compressed and packed files in particular are often flagged as suspicious by security software because they have difficulty reading what is inside them. These detections do not necessarily mean the file is malware or a bad program.

It means it has the potential for being misused by others or that it was simply detected as suspicious or a threat due to the security program's heuristic analysis engine which provides the ability to detect possible new variants of malware. Anti-virus scanners cannot distinguish between "good" and "malicious" use of such programs, therefore they may alert you or even automatically remove them. In these cases the detection is a "false positive".

The problem is really with the anti-vendors who keep targeting these embedded files and NOT with ComboFix. We can inform the developer but he has encountered this issue before and in most cases there isn't much he can do about it.
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