When I scanned a system with ClamWin 0.90.1, it reported that the executable opera.exe for the Opera web browser was infected with Trojan.Bifrose-495. The system has Opera 8.54 on it.
Checking the definitions timestamp in ClamWin, I saw the following:
Protecting from 107238 Viruses
Virus DB Version: (main: 42, daily: 3049)
Updated: 18:49 08 Apr 2007
I found someone else reporting the same problem on a ClamWin support forum at False Positives. And I found a post, Opera.exe: Trojan.Bifrose-495 FOUND, on an Opera community forum site, where someone posted that ClamAV reported "Trojan.Bifrose-495 FOUND" for opera.exe, though in his case it appeared he had version 7 of Opera on his system. He submitted opera.exe from his system to VirusTotal, which provides a free service allowing you to upload a file for analysis by many different antivirus programs. Only ClamAV and Fortinet identified the file as being suspicious. The other 27 antivirus scanners used by VirusTotal reported it was uninfected. ClamWin is a Windows implementation of ClamAV.
There was also another posting, Trojan.Bifrose-495? in a ClamWin forum where someone stated that ClamWin 0.88.7 reported the same infection for his copy of opera.exe. One of the ClamWin developers, sherpya, responded that it was a false positive. That person also submitted his copy to VirusTotal. The result was the same for him, with only ClamAV reporting the file as infected and Fortinet labelling it as "suspicious".
I found someone else reporting that ClamWin reported Opera was infected with Trojan.Bifrose-495 at Cleaning up a trojan, but the poster didn't appear to consider the possibility that the report may have been a false positive.
I submitted the opera.exe file from my system to VirusTotal also. One of the ClamWin developer's referred the person who posted at False Positives on the ClamWin forum to How can I report a virus that ClamWin doesn't recognise? Or a false positive?, which also suggests submitting the file to VirusTotal , if you suspect that ClamWin is reporting a false positive. The file was scanned by 23 antivirus programs. Only ClamAv and Fortinet reported an issue with the file. ClamAv reported it found "Trojan.Bifrose-495", while Fortinet reported the file as "suspicious".
I also submitted the file to Jotti's Malware Scan, which also provides a free virus scanning service. Of the 17 antivirus programs it uses, only ClamAv reported the file as infected with ClamAv reporting "Found Trojan.Bifrose-495". It scanned the file with Fortinet as well, but reported for Fortinet that "Found nothing" (see report ).
I did submit the file using the on-line form at ClamAV Virus Database as a false positive.
So what does Trojan.Bifrose-495 do? I don't know and could not find any information on it via a Google search. Though I really like ClamWin and ClamAV, using them on many systems, one major advantage I see to a program like Symantec's antivirus software, aside from real-time scanning, is that Symantec will provide you with details on how most of the viruses it identifies work. By looking at the provided details, you can determine, if your system was infected, what the virus or trojan may have done and what other indicators of the infection you should expect to find on the system. ClamAV and thus ClamWin, which is built on ClamAV, provide no virus encyclopedia you can use for reference. If this wasn't a false positive I would certainly like to know how the virus or trojan operates, not just a name for it. Does it allow someone to take remote control of the infected system? Does it send out spam from the system, delete or corrupt files, etc.?
I normally use ClamWin as an adjunct to other antivirus software on a system and don't want real-time scanning capability from it, but really would like to have further details on any infections found. I have found ClamWin identifies malware other antivirus programs sometimes miss and am very appreciative of the work done by the developers for both ClamAV and ClamWin, but, whenever they report an infected file, I often have to submit the file to VirusTotal or Jotti's Malware Scan to attempt to figure out the potential harm that may have been caused by an infection. I look at the names used for the infection by other antivirus programs that also report the submitted file is infected. I then look check virus encyclopedias they may provide or do further searching of the web using the names they use for the malware.
Details for the file I submitted:
|Size:||76.5 KB (78,336 bytes)|
|Created:||Saturday, April 15, 2006, 1:34:26 PM|
|Modified:||Friday, March 24, 2006, 5:40:10 PM|
|Product Name:||Opera Internet Browser|
The modification date listed on the file when I right-clicked on it and chose Properties was March 24, 2006. I installed Opera 8.54 on the system on April 15, 2006, so the modification date listed is several weeks prior to the software being installed on the system.
I also scanned the file with BitDefender 8 Free Edition, which had virus definitions of April 8, 2007, which is today's date, and Symantec AntiVirus Corporate Edition 8, which had virus definitions from April 4, 2007. Both of those antivirus programs were on the system where I ran the ClamAV scan. Both reported the file was uninfected, so I'm fairly confident at this point that ClamAV's report of the file as infected was a false positive.
Posted February 11, 2006
ClamWin Free Antivirus Support and Discussion Forums
Opera.exe: Trojan.Bifrose-495 FOUND
Posted: December 20, 2006
Forums - Opera Community
January 5, 2007
ClamWin Free Antivirus Support and Discussion Forums
Cleaning up a trojan
December 21, 2006