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Possible Trojan, but possible false positive... How can I ensure I'm clean?


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#1 Tetranitrocubane

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Posted 14 December 2008 - 10:45 AM

Hi everyone. I'm new about the board, so sorry for barging in with a problem... But I'm just unsure of myself at the moment and really could use some other opinions!

I currently run a system that has Windows XP professional SP3. It's patched up to date with the latest Windows Updates. I also run Eset's NOD32 for my anti-virus software, though I admit I'm still using version 2.70 instead of the later ones. I keep NOD up to date as well, and it usually keeps the virus definitions updated at least once a day, if not more. Also, and this is the important bit, a few months ago I used to play a game. I used to play Phantasy Star Online through a private server called Schthack. It was several months ago that I installed and played the game, and I've not touched it in some time. According to several sources, the private server version of the game sometimes calls up false positives. NOD never has had any problems with it...

... Until two days ago. When running the weekly scan, NOD suddenly flagged the PsoBB.exe part of Phantasy Star Online as a virus. Specifically it labeled it as a Trojan, a Win32/Kryptik.CR variant. I was a little bit scared to see that, particularly since it had been on my computer for so long without issue. I suppose the latest definitions are what keyed NOD off to PSO - But I'm not sure if it was a false positive or not, as it was reported to be in the past on other AV scanners.

I hardly ever play the game any longer, so I willingly uninstalled it and ensured all the files were purged. Running another system scan after this brought back no threats or infected files, so I was resting a little easier. Until the following morning when I suddenly received this message from NOD's AMON module:

-----

File:
C:\System Volume Information\_restore{620C87CB-71F6-4074-8232-90F..\A0071163.exe

Threat: a variant of Win32/Kryptik.CR trojan

Comment:
Event occured on a file modified by the application C:\Windows\System32\svchost.exe. The file was moved to quarantine. You may close this window.

-----

I was more concerned at this point. However, I came to think that perhaps it was just a reminant of the PsoBB.exe file in a System Restore point, so I purged the system restore, made a fresh restore point afterward, and ran another scan that came back clean. I also followed it up with a run from an updated version of SpyBot S&D, which turned up nothing but cookies. A quick auto-analysis of a Hijackthis log came back clean too.

Since then I haven't noticed anything else that has me concerned, except for an event when Trillian dropped my AIM connections and positively refused to allow me to reconnect - but that may have been a very isolated incident, I think, and it was resolved by killing the connection to AIM servers with TCIP/IPview.

Anyhow, I'm very nervous, because I don't see how something that was a false positive could wind up in my system restore and infect files there, if it wasn't an actual trojan. However, I'm at a loss as to the next steps to take to determine whether or not I am actually infected. Any assistance would be greatly appreciated on this issue! Thank you in advance.

P.S. I work a pretty horrendous schedule, so it might take me a while to update progress once a day or so.

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#2 quietman7

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Posted 14 December 2008 - 02:48 PM

It is not uncommon for subsequent scanning after updates of a particular security product has been released to result in detection of items which had previously gone undetected by prior scans.

The infected RP***\A00*****.exe/.dll file(s) identified by your scan are in the System Volume Information Folder (SVI) which is a part of System Restore. This is the feature that allows you to set points in time to roll back your computer to a clean working state. The SVI folder is protected by permissions that only allow the system to have access and is hidden by default unless you have reconfigured Windows to show it.

System Restore will back up the good as well as the bad files so when malware is present on the system it gets included in any restore points as an A00***** file. When you scan your system with anti-virus or anti-malware tools, they may detect and place these files in quarantine. When a security program quarantines a file, that file is essentially disabled and prevented from causing any harm to your system. The quarantined file is safely held there and no longer a threat. Thereafter, you can then delete it at any time.

If the anti-virus or anti-malware tool cannot move the files to quarantine, they sometimes can reinfect your system if you accidentally use an old restore point. To remove these file(s), the easiest thing to do is Create a New Restore Point to enable your computer to "roll-back" to a clean working state and use Disk Cleanup to remove all but the most recent restore point.
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#3 Tetranitrocubane

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Posted 15 December 2008 - 03:56 PM

Thanks for the input! I really do appreciate it. I understand that System Volume Information is a part of the System restore - This is exactly why I purged the previous restore points, made a new one, and rescanned my system. I even reconfigured Windows to allow access and scanned the files directly, before protecting them again.

I am merely concerned that NOD may be missing something. The fact that it got through a second time is worrisome to me. Additionally, I'm not sure why a false positive (as I have been told it is in the past) would be there.

As an UPDATE to my situation, the computer seems to be freezing now. This has never happened before. I think that it is no coincidence, and I'm inclined to think that this was not a false positive after all. However, NOD32 seems to come up empty handed, even in safe mode. Are there any other steps that I can take that will not damage my computer in order to check to ensure it is not infected? I was looking into combofix, but that seems dangerous to use. Thanks again!

#4 quietman7

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Posted 16 December 2008 - 08:26 AM

I am merely concerned that NOD may be missing something. The fact that it got through a second time is worrisome to me.

No single product is 100% foolproof and can detect and remove all threats at any given time. The security community is in a constant state of change as new infections appear. Each vendor has its own definition of what constitutes malware and scanning your computer using different criteria will yield different results. The fact that each program has its own definition files means that some malware may be picked up by one that could be missed by another. Thus, a multi-layered defense using several anti-spyware products (including an effective firewall) to supplement your anti-virus combined with common sense and safe surfing habits provides the most complete protection.

Additionally, I'm not sure why a false positive (as I have been told it is in the past) would be there.

It is not uncommon for subsequent scanning after updates of a particular security product has been released to result in detection of items which had previously gone undetected by prior scans. This could even result in a FP.

I was looking into combofix, but that seems dangerous to use.

Please note the message text in blue at the top of this forum.

You should not be using Combofix unless 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", NOT for private use. Using this tool incorrectly could lead to disastrous problems with your operating system such as preventing it from ever starting again. Please read Combofix's Disclaimer.

Please download Malwarebytes Anti-Malware and save it to your desktop.
alternate download link 1
alternate download link 2
  • Make sure you are connected to the Internet.
  • Double-click on mbam-setup.exe to install the application.
  • When the installation begins, follow the prompts and do not make any changes to default settings.
  • When installation has finished, make sure you leave both of these checked:
    • Update Malwarebytes' Anti-Malware
    • Launch Malwarebytes' Anti-Malware
  • Then click Finish.
MBAM will automatically start and you will be asked to update the program before performing a scan.
  • If an update is found, the program will automatically update itself.
  • Press the OK button to close that box and continue.
  • If you encounter any problems while downloading the updates, manually download them from here and just double-click on mbam-rules.exe to install. Alternatively, you can update through MBAM's interface from a clean computer, copy the definitions (rules.ref) located in C:\Documents and Settings\All Users\Application Data\Malwarebytes\Malwarebytes' Anti-Malware from that system to a usb stick or CD and then copy it to the infected machine.
On the Scanner tab:
  • Make sure the "Perform Quick Scan" option is selected.
  • Then click on the Scan button.
  • If asked to select the drives to scan, leave all the drives selected and click on the Start Scan button.
  • The scan will begin and "Scan in progress" will show at the top. It may take some time to complete so please be patient.
  • When the scan is finished, a message box will say "The scan completed successfully. Click 'Show Results' to display all objects found".
  • Click OK to close the message box and continue with the removal process.
Back at the main Scanner screen:
  • Click on the Show Results button to see a list of any malware that was found.
  • Make sure that everything is checked, and click Remove Selected.
  • When removal is completed, a log report will open in Notepad.
  • The log is automatically saved and can be viewed by clicking the Logs tab in MBAM.
  • Copy and paste the contents of that report in your next reply and exit MBAM.
Note: If MBAM encounters a file that is difficult to remove, you may be asked to reboot your computer so it can proceed with the disinfection process. Regardless if prompted to restart the computer or not, please do so immediately. Failure to reboot normally (not into safe mode) will prevent MBAM from removing all the malware. MBAM may "make changes to your registry" as part of its disinfection routine. If using other security programs that detect registry changes (ie Spybot's Teatimer), they may interfere or alert you after scanning with MBAM. Please temporarily disable such programs or permit them to allow the changes.
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#5 Tetranitrocubane

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Posted 16 December 2008 - 03:02 PM

Thank you for your prompt and informative post. That makes a lot of sense, and I really appreciate your taking the time to help me out, and particularly for alerting me to the dangers of using Combofix without help!

I followed the instructions as you requested, and the log file from MBAM gave the following log file with one infected instance. I think this is detritus from the earlier infection, but I'll leave the analysis to the experts!

Malwarebytes' Anti-Malware 1.31
Database version: 1507
Windows 5.1.2600 Service Pack 3

12/16/2008 11:59:19 AM
mbam-log-2008-12-16 (11-59-19).txt

Scan type: Quick Scan
Objects scanned: 51751
Time elapsed: 3 minute(s), 16 second(s)

Memory Processes Infected: 0
Memory Modules Infected: 0
Registry Keys Infected: 0
Registry Values Infected: 0
Registry Data Items Infected: 0
Folders Infected: 0
Files Infected: 1

Memory Processes Infected:
(No malicious items detected)

Memory Modules Infected:
(No malicious items detected)

Registry Keys Infected:
(No malicious items detected)

Registry Values Infected:
(No malicious items detected)

Registry Data Items Infected:
(No malicious items detected)

Folders Infected:
(No malicious items detected)

Files Infected:
C:\Documents and Settings\John\_online.exe (Trojan.FakeAlert) -> Quarantined and deleted successfully.

#6 quietman7

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Posted 16 December 2008 - 03:25 PM

Lets do another scan to see if we find anything else that MBAM may have missed.

Please download ATF Cleaner by Atribune & save it to your desktop. DO NOT use yet.
alternate download link

Please download and install SUPERAntiSpyware Free
  • Double-click SUPERAntiSypware.exe and use the default settings for installation.
  • An icon will be created on your desktop. Double-click that icon to launch the program.
  • If asked to update the program definitions, click "Yes". If not, update the definitions before scanning by selecting "Check for Updates". (If you encounter any problems while downloading the updates, manually download them from here. Double-click on the hyperlink for Download Installer and save SASDEFINITIONS.EXE to your desktop. Then double-click on SASDEFINITIONS.EXE to install the definitions.)
  • In the Main Menu, click the Preferences... button.
  • Click the "General and Startup" tab, and under Start-up Options, make sure "Start SUPERAntiSpyware when Windows starts" box is unchecked.
  • Click the "Scanning Control" tab, and under Scanner Options, make sure the following are checked (leave all others unchecked):
    • Close browsers before scanning.
    • Scan for tracking cookies.
    • Terminate memory threats before quarantining.
  • Click the "Close" button to leave the control center screen and exit the program.
  • Do not run a scan just yet.
Reboot your computer in "Safe Mode" using the F8 method. To do this, restart your computer and after hearing your computer beep once during startup (but before the Windows icon appears) press the F8 key repeatedly. A menu will appear with several options. Use the arrow keys to navigate and select the option to run Windows in "Safe Mode".

Double-click ATF-Cleaner.exe to run the program.
  • Under Main "Select Files to Delete" choose: Select All.
  • Click the Empty Selected button.
  • If you use Firefox browser click Firefox at the top and choose: Select All
  • Click the Empty Selected button.
    If you would like to keep your saved passwords, please click No at the prompt.
  • If you use Opera browser click Opera at the top and choose: Select All
  • Click the Empty Selected button.
    If you would like to keep your saved passwords, please click No at the prompt.
  • Click Exit on the Main menu to close the program.
Note: On Vista, "Windows Temp" is disabled. To empty "Windows Temp" ATF-Cleaner must be "Run as an Administrator".

Scan with SUPERAntiSpyware as follows:
  • Launch the program and back on the main screen, under "Scan for Harmful Software" click Scan your computer.
  • On the left, make sure you check C:\Fixed Drive.
  • On the right, under "Complete Scan", choose Perform Complete Scan and click "Next".
  • After the scan is complete, a Scan Summary box will appear with potentially harmful items that were detected. Click "OK".
  • Make sure everything has a checkmark next to it and click "Next".
  • A notification will appear that "Quarantine and Removal is Complete". Click "OK" and then click the "Finish" button to return to the main menu.
  • If asked if you want to reboot, click "Yes" and reboot normally.
  • To retrieve the removal information after reboot, launch SUPERAntispyware again.
    • Click Preferences, then click the Statistics/Logs tab.
    • Under Scanner Logs, double-click SUPERAntiSpyware Scan Log.
    • If there are several logs, click the current dated log and press View log. A text file will open in your default text editor.
    • Please copy and paste the Scan Log results in your next reply.
  • Click Close to exit the program.

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