Trojan-Downloader:W32/Agent.ETO

Classification

Malware

Trojan-Downloader

W32

Trojan-Downloader:W32/Agent.ETO

Summary

Initially associated with the most recent PDF exploit malware run that we detect as Exploit:W32/AdobeReader.L, Agent.ETO normally arrives as a dropped/downloaded malware component by other malware running in the infected system. Upon execution, it drops/downloads and executes several other trojans on the system.

Removal

Automatic action

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

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Submit a sample

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Technical Details

Based on the system OS version, the malware will overwrite any of the following files; with another trojan embedded in its resource section:

  • ip6fw.sys
  • netdtect.sys
  • secdrv.sys

This newly created trojan is detected as Trojan-Downloader:W32/Agent.ACL . It is then executed as a Driver service using the Service Control Manager, thus further compromising the system.The malware will then drop yet another malicious file in the system as:

  • %system%\drivers\runtime.sys

This new driver will then be loaded and executed using a native call to NtLoadDriver after adjusting necessary system privileges needed to perform such commands. This new sys file is detected by F-Secure products as Trojan-Downloader:W32/Agent.DPE.Due to this actions, the following registry associated with the malware will be created:

  • HKLM\System\CurrentControlSet\Services\Runtime
  • HKLM\System\CurrentControlSet\Services\Runtime
  • ImagePath= "\??\%system%\drivers\runtime.sys"

Note: %system% refers to the default windows System directory, it is usually c:\Windows\System32.Such that the above registry becomes:

  • ImagePath="\??\C:\windows\system32\drivers\runtime.sys"

Lastly, using a hidden "browser" process (e.g. iexplore.exe, firefox.exe), it will inject another malware executable image in that process space to enable downloading other malicious files into the user system. Using this approach, it ensures that the downloader component will be able to do its job, since it is most likely that the user's internet browser is allowed to pass through the system firewall.This injected image, is then responsible for downloading other files from remote servers and executing it in the compromised system. As of current testing, the download files is detected as:

  • Rootkit.Win32.Agent.EY