Threat Descriptions

Netlog

Classification

Category :

Malware

Type :

Worm

Platform :

VBS

Aliases :

Netlog, Network.vbs

Summary

VBS/Netlog is a worm written with Visual Basic Script.

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

Variant:Netlog.A

When executed, VBS/Netlog creates a log file, "c:\network.log" and writes the following line to it: 

Log file Open

Then the worm enters in an infinite loop. The worm begins the loop with the generation of a random IP class C subnet address. At first the first number of the IP address is a random number between 199 and 214, but after 50 iterations in the loop the number range is from 1 to 254. Second and third numbers of the IP address are always between 1 and 254. After the IP address has been generated the worm writes this to its log file: 

Subnet
:
*.*.*.0

where an asterisk ("*") is replaced with a number.

The VBS/Netlog goes trough the entire subnet address space (1-254) and looks a share named "C" from each machine. This is the default name for a shared "C:" drive.

If the share is found, the worm maps the remote drive to local machine as "J:" drive and adds one line to the log file: 

Copying files to
:
\\*.*.*.*\C

Then it copies itself to the following locations in the remote share: 

j:\network.vbs

 j:\windows\network.vbs

 j:\windows\start menu\programs\startup\network.vbs

 j:\win95\start menu\programs\startup\network.vbs

 j:\win95\startm~1\programs\startup\network.vbs

 j:\wind95\network.vbs

By doing this it infects the remote machine. When the remote machine is restarted, the worm will be executed.

The following line will be added to the log file if files were copied: 

Successfull copy to
:
\\*.*.*.*\C

Finally the worm takes the next address in the subnet, or chooses the next random IP address and starts again.

Variant:Netlog.B

This variant consists of two files. It copies itself only to: 

C:\windows\start menu\programs\startup\network.vbs

 C:\windows\start menu\programs\startup\network.exe

It maps the remote drive to local machine as "Z:" (not "J:" as the VBS/Netlog.A variant does).

When it creates the log file "c:\network.log", the added line is different as well: 

Copyright (c) 1993-1995 Microsoft Corp.