Threat Descriptions

Net-Worm:W32/Nimda.E

Classification

Category :

Malware

Type :

Net-Worm

Platform :

W32

Aliases :

Nimda.E, W32/Nimda.e@mm, Net-Worm.Win32.Nimda.e

Summary

Net-Worm:W32/Nimda.E is a recompiled variant of Net-Worm:W32/Nimda.A.

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

Net-Worm:W32/Nimda.E is not compressed. It uses the same techniques as Nimda.A, except it spreads itself with SAMPLE.EXE file name.

Other minor differences are as follows:

  • The worm uses COOL.DLL name to upload itself to webservers
  • The worm uses HTTPODBC.DLL name to start from on servers
  • The worm uses CSRSS.EXE name to copy itself to servers

This version of Nimda has few serious bugs that allow it to infect files several times and to jam NT systems considerably.

On October 30th, F-Secure received reports of live infections in Germany and Sweden. On October 31st, we received further reports from USA, China, France, Norway, Finland and Spain.

Apparently the author of Nimda was offended because his virus wasn't named "Concept Virus" like he wanted. The virus code contains a copyright text string which is never displayed, saying "Concept Virus(CV) V.6, Copyright(C)2001, (This's CV, No Nimda.)"

The actual lifecycle of Nimda can be split to four parts:

  • Infecting files
  • Mass mailing
  • Web worm
  • LAN propagation