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Combofix is suddenly an trojan , according to Avast.


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#1 Mrk23

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Posted 02 August 2014 - 02:46 PM

I was about to scan my computer with Combofix (since i had a lot of outbound traffic with skype for some reason (blocked connections every minute) ) , but when I tried to open Combofix , it first said something about an NSIS error. I did what Combofix told me to do , going to a site that helped me to get the file complete. I removed my history and everything , and the file came in fully. But , when I opened Combofix.exe (from Bleepingcomputer) , Avast! told me this:

AutoIt:Banker-BG [Trj]

 

I thought , maybe I just downloaded the wrong file. So I re-downloaded it , but nothing goods.

 

When I scanned ComboFix (1).exe on Virustotal , other Antiviruses detected it as virus too , and it looked like it was an whole new file since it said it was first scanned around 2014 , and the program exists longer.

https://www.virustotal.com/en/file/de544972c0d5f934f0ca27e6d63e665641f87037f810b7a3f185bf428f2fc61a/analysis/1407007306/

(only 1 rating too , and it was not a good rating...)

 

 

I re-scanned the old file i have on this laptop (downloaded 7-21-2014) , and Virustotal told me this:

https://www.virustotal.com/en/file/fbbe1f51f8fa9fc88e8572a5dd111503802654f33f80e10f7ecde6e53f2a23a3/analysis/1407008723/

 

(again , only 1 rating and it was bad , again.)

 

I'm now scanning the laptop with Malwarebytes PRO (full scan on both drives + rootkit scan) , but im still worried.

I Avast just giving me an false positive or is the ComboFix file really infected , or is my laptop infected?

 

 

(Adding this:

I have Windows 7 Home Premium SP1

My antivirus is Avast! , along side with Malwarebytes PRO)


Edited by Mrk23, 02 August 2014 - 02:50 PM.


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#2 quietman7

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Posted 02 August 2014 - 07:41 PM

This is a false positive by the anti-virus.

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 suspicious, a Risk Tool, Hacking Tool, Potentially Unwanted Program, a possible threat 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 (routines, scripts, etc) 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.

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 malicious 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" and can be ignored. Either have your anti-virus ignore the detection or temporarily disable it until you download and run the tool.

The problem is really with the anti-virus vendors who keep targeting these embedded files and NOT with ComboFix. We can inform the developer but he has encountered this issue many times before and in most cases there isn't much he can do about it. Once the detection is reported to the anti-virus vendor, they are usually quick to fix it by releasing an updated definition database.
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#3 Rayezilla

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Posted 04 August 2014 - 09:28 AM

It's relatively common to see antiviruses target other antivirus software. If you think about it, anti virus software inserts itself into many critical components in much the same way that a virus would. This is part of the reason that running two anti viruses together is so ineffective. 



#4 quietman7

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Posted 04 August 2014 - 04:23 PM

ComboFix is not an anti-virus...it is a specialized tool for 1st responders.
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