This variant of the Nyxem worm was found in September 2004. The worm spreads itself via emails. It deletes files of various security applications.
F-Secure's F-Force disinfection program can be used to clear a Nyxem.E infection. The tool can be downloaded from our web and ftp sites:
The utility is distributed only in a ZIP archive that contains the following files:
To unpack the archive please use the WinZip or similar archiver.
Please make sure that you read the End User License Terms document (Eult.rtf) and the Readme file (either Readme.txt or Readme.rtf) before using the F-Force utility!
The F-Force utility needs the archive with the latest updates in order to function properly. The archive's name is LATEST.ZIP and it should be downloaded and put into the same folder where the F-Force utility is located. This archive with the latest updates can be downloaded from these locations:
Please note that the F-Force utility can disinfect only certain malicious programs. Besides the utility does not scan inside archives. So after cleaning a computer with the F-Force utility it is recommended to scan all hard drives with F-Secure Anti-Virus and the latest updates to make sure that no infected files remain there.
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.
Nyxem.E is similar to Email-Worm.Win32.VB.bi.
The worm has the following text strings in its body:
Nyxem.E is written in Visual Basic and is compiled as p-code. The size of the main executable is about 95 kilobytes.
When the worm's file is run, it first opens WinZip as a decoy. It may also block keyboard and mouse input to force the user to press CTRL + ALT + DEL and log off.
During the installation phase the worm copies its file to several locations:
where '%Windows%' indicates the main Windows folder (usually C:\WINDOWS\) and '%System%' is the Windows System folder.
The worm has a dangerous payload. If the date is equal to 3 (3rd of February, 3rd of March, etc) and the worm's UPDATE.EXE file is run, it destroys files with those extensions on all available drives:
The files' contents are replaced with a text string "DATA Error [47 0F 94 93 F4 K5]".
The payload is activated 30 minutes after the worm's file UPDATE.EXE is loaded into memory (basically 30 minutes after logon).
When the payload is activated, the worm enumerates all logical drives and damages files on them in a loop. It should damage files on all drives that have a letter. Files on local and removable drives (including USB memory) are also damaged. This should also apply to network drives, but during testing the worm failed to do affect them.
The worm attempts to disable several security-related and file sharing programs. It deletes startup key values from the Registry if they contain any of the following:
The following startup Registry keys are affected:
The worm deletes files from the following subfolders in the Program Files folder:
In addition the worm reads location of certain programs from Windows Registry and deletes certain files in these locations. The affected software is:
The worm also closes application windows that have the following strings in their captions:
For some reason the worm adds several license keys to the Registry. Most of them seem to belong to VB6 controls. Also the worm makes changes to the registry.
The worm can modify Active Desktop files in order to launch another copy of itself named 'WinZip_Tmp.exe' using the ActiveX control.
Whenever the worm infects a computer it opens a web browser on a certain webpage. This increments an infection counter on that webpage.
We were contacted by the organization that runs the site with that counter. They informed us that the counter readings were not accurate. There were multiple hits from the same IPs to the counter.
According to the latest information we received, the number of hits from unique IPs is over 300000 which is still quite big.
The worm collects email addresses from files with following extensions:
The worm searches for files with these extensions in Internet Explorer cache folders. email addresses that have any of the following substrings are ignored by the worm:
The worm sends itself as attachment in the infected email. The email subject can be one the following:
The message body may be one of the following:
The worm usually attached itself to email messages as an executable file. It uses one the following names in attachment:
Sometimes, the worm MIME-encodes the file. In these cases, the attachment name can be one of the following:
The filename inside MIME-encoding is one of the following:
The worm has several network spreading routines. One of them enumerates all available shares, then reads the values of the following registry keys:
The above registry key values point to user's folders where personal documents and recently opened files are stored.
If a matching folder is found, the worm opens it, enumerates files there, "borrows" one randomly selected file name and adds an EXE extension to it. Then the worm copies itself to network shares using the newly created name.
If the worm does not find any files in those folders, it copies itself to network shares with the following names:
The other network spreading routine searches for specific network shares and tries to copy itself using one of the following filenames:
At the same time the worm deletes the following file:
Before spreading the worm checks whether a remote computer has any of the following folders and if it does, the worm tries to delete all files from that folder:
The worm also creates a scheduled task to run the worm's files on remote computer with system priviledges at the 59th minute of the current hour.
Creates these keys: