Threat Descriptions

Trojan:W32/Lecpetex

Classification

Category :

Malware

Type :

Trojan

Platform :

W32

Aliases :

Trojan:W32/Lecpetex, Trojan.Lecpetex

Summary

Trojan:W32/Lecpetex silently downloads and runs a file that performs Bitcoin mining using the user's system.

Removal

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.

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 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.

Technical Details

Lecpetex is distributed in a malicious zipped file sent out as attachments to Facebook messages.

Screenshot of Facebook message used to distribute Lecpetex

The zipped file contains a JAR file that executes when the user clicks on the attachment. It then downloads a binary file from the Dropbox filesharing service to the temp file of the user's system; the downloaded file uses a random name.

The JAR file then executes the downloaded binary file using regsvr32.exe, using /s switch to do so silently without displaying any message boxes. It also creates a copy of itself as a hidden file at the following location:

  • C:\\temp:{random}.dat

And creates a launch point with the following registry. In addition, it creates a bogus registry entry to help keep this launch point hidden from a registry editor.

  • [Launch Point] SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run regsvr32 /s "c:\\temp:%w+.dat

It also creates another two instances of explorer and injects its code into these processes to serve as watchdog processes, making sure that the launch point will always be in the system.

Lecpetex's ultimate aim is to launch an instance of explorer.exe, then download a binary file that runs in the memory of explorer.exe in order to mine Bitcoins.

Trojan:W32/Lecpetex is written in C++.