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Combofix Executable Infected?


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#1 Jarrend

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Posted 20 November 2011 - 04:03 AM

Uploaded latest Combofix.exe (downloaded from BleepingComputer.com) to VirusTotal. One of the scanners shows file is infected by "Backdoor/RBot.oqm".

http://www.virustotal.com/file-scan/report.html?id=189f4b871d7eed501cd3930e9b918d756443b9eb0d56d632288ca3475ef6ce05-1321778670

Unable to find any useful information about "Backdoor/RBot.oqm." Is this a false positive?

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#2 Andrew

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Posted 20 November 2011 - 04:54 AM

Combofix if regularly flagged by some antivirus tools. This is largely due to the fact that many of the methods it uses to dis-infect a computer are the same methods commonly used to infect it in the first place.

So, provided you downloaded it from this URL: http://www.bleepingcomputer.com/download/anti-virus/combofix you can assume that the detections are false positives.

#3 quietman7

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Posted 21 November 2011 - 03:27 PM

Expanding on what Andrew has said.

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.

IMPORTANT!: If you ran or want to run ComboFix on your own due to malware infection, please be aware that using it is only one part of the disinfection process. Preliminary scans from other tools like DDS, RSIT and GMER should be used first because they provide comprehensive logs with specific details about files, folders and registry keys which may have been modified by malware infection. Analysis of those logs allows planning an strategy for effective disinfection and a determination if using ComboFix is necessary.

Further, when issues arise due to complex malware infections, possible false detections, problems running ComboFix or with other security tools causing conflicts, 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.

ComboFix was never meant to be used as a general purpose malware scanner like SuperAntispyware or Malwarebytes' Anti-Malware which scan individual drives or different folders on a computer for viruses. Using this tool incorrectly could lead to disastrous problems with your operating system such as preventing it from ever starting again. Please read the pinned topic ComboFix usage, Questions, Help? - Look here.
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