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Preims.dll False Positive


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Prior to this post, I endeavored to run a scan in "developer mode" but the "mbam.exe /developer" command simply opened the Malwaretyes main screen.

I ran the scan but do not see any difference between the resulting log (included near the end of this post and identified as 4/25/09 5:10:22 am) and a log from a Malwarebytes scan when running in "normal" mode.

In scans over the past week (such as the 4/16/09 scan below), Malwarebytes has found a file named "preims.dll" in the C:\Windows folder and identified it as a "Trojan.Agent".

===========================================

Malwarebytes' Anti-Malware 1.36

Database version: 1989

Windows 5.1.2600 Service Pack 3

4/16/2009 3:48:37 AM

mbam-log-2009-04-16 (03-48-37).txt

Scan type: Full Scan (C:\|E:\|F:\|G:\|)

Objects scanned: 140373

Time elapsed: 17 minute(s), 28 second(s)

Memory Processes Infected: 0

Memory Modules Infected: 1

Registry Keys Infected: 0

Registry Values Infected: 1

Registry Data Items Infected: 4

Folders Infected: 0

Files Infected: 3

Memory Processes Infected:

(No malicious items detected)

Memory Modules Infected:

C:\WINDOWS\preims.dll (Trojan.Agent.W) -> Delete on reboot.

Registry Keys Infected:

(No malicious items detected)

Registry Values Infected:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\fbupegeqeluwen (Trojan.Agent) -> Quarantined and deleted successfully.

Registry Data Items Infected:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA\Notification Packages (Trojan.Vundo.H) -> Data: preims.dll -> Quarantined and deleted successfully.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center\AntiVirusDisableNotify (Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Not selected for removal.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center\FirewallDisableNotify (Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Not selected for removal.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center\UpdatesDisableNotify (Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Not selected for removal.

Folders Infected:

(No malicious items detected)

Files Infected:

C:\WINDOWS\preims.dll (Trojan.Vundo.H) -> Delete on reboot.

C:\Documents and Settings\Tom Gunby\Local Settings\Temp\tmp3077.tmp.exe (Trojan.Agent.W) -> Quarantined and deleted successfully.

C:\WINDOWS\afunoguqutoqih.dll (Trojan.Agent) -> Delete on reboot.

======================================

I instructed Malwarebytes to remove the "preims.dll" file which it did on reboot, however, "preims.dll" returned in a day or two.

I again instructed Malwarebytes to remove the "preims.dll" file, which it did on reboot, but "preims.dll" returned in another day or two.

Before running a scan today, I checked C:\Windows folder and can see the "preims.dll" file in the c:\windows folder.

However, a scan today (see below) with Malwarebytes (run in both normal mode and safe mode) did not identify the "preims.dll" file as a Trojan nor offer to remove it.

=====================================

Malwarebytes' Anti-Malware 1.36

Database version: 2039

Windows 5.1.2600 Service Pack 3

4/25/2009 5:10:22 AM

mbam-log-2009-04-25 (05-10-22).txt

Scan type: Full Scan (C:\|E:\|F:\|G:\|)

Objects scanned: 143388

Time elapsed: 20 minute(s), 59 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: 0

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:

(No malicious items detected)

=====================================

I have not instructed Malwarebytes to "ignore" the "preims.dll" file so I am wondering if the original identification of "preims.dll" as malware was a false positive.

Please explain.

Thank you.

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  • Staff

Hi,

This is no false positive. Detection is based on heuristics here, which may explain why it isn't detected if inactive. But I'm 100% sure this file is no false positive. Most scanners will flag this file as Trojan Hiloti.

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Thank you for the prompt response.

If preims.dll is indeed malware but not identified by Malwarebytes (or a HijackThis scan), how then do I remove preims.dll not only from c:\windows but from wherever it is being called at system startup?

I looked in the "run" key in the registry but did not find a line that starts preims.dll.

Thank you.

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  • Staff

Hi,

If preims.dll is indeed malware but not identified by Malwarebytes (or a HijackThis scan)
HijackThis won't identify any malware, it just enumerates startup entries in the registry and their related files. HijackThis doesn't know the difference between malware and legitimate programs/files.
how then do I remove preims.dll not only from c:\windows but from wherever it is being called at system startup?
MalwareBytes already removed the reference in the registry - which explains why it doesn't find the file anymore, so to delete the file, you have to navigate to C:\Windows\preims.dll and delete it manually. If you can't delete it - reboot and try again. (This because it may be still hooked in case you didn't reboot previously after the malwarebytes scan). If you're still having problems with deleting or it comes back, then it means that something else is still present there. In that case, Scan and post logs - read note at bottom in green

If you're having Malware related issues with your computer that you're unable to resolve.

  1. Please read and follow the instructions provided here: I'm infected - What do I do now?
  2. If needed please post your logs in a NEW topic here: Malware Removal - HijackThis Logs
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  • Please do not install any software or use any removal/scanning tool except for those you're requested to run by the Helper that will assist you.
  • Using these other tools often makes the cleanup task more difficult and time consuming.
  • If you have already submitted for assistance at one of the other support sites on the Internet then you should not post a new log here, you should stay working with the Helper from that site until the issue is resolved.
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  • There are often many others that require asistance as well, so please be patient. If no one has responded within 48 hours then please go ahead and post a request for review
  • NOTE: If for some reason you're unable to run some or any of the tools in the first link, then skip that step and move on to the next one. If you can't even run HijackThis, then just proceed and post a NEW topic as shown in the second link describing your issues and someone will assist you as soon as they can.
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