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This type of worm is embedded in an email attachment, and spreads using the infected computer's emailing networks.


Disinfection of the Luder virus-worm should be performed as follows:

  • Disconnect a computer or local network from the Internet.
  • Disable network sharing or set strong passwords for all shared computers.
  • Select the "Disinfect Automatically" action for F-Secure Anti-Virus real-time scanners on all computers. With "Disinfect Automatically" selected, F-Secure Anti-Virus will disinfect files that a virus tries to infect over a network (if sharing was not disabled) or on local drives (if the virus is active in memory).
  • Scan ALL files on all the computer drives and MANUALLY select the "Disinfect" action to disinfect all infected files and rename the virus droppers and downloaders. DO NOT select Automatic Cleaning option after the scan (see CAUTION below).
  • Restart all disinfected computers.
  • Scan all hard drives on disinfected computers again to make sure that no more infected files are left. If needed, repeat the disinfection procedure.
  • Disinfect all infected computers connected to the network.
  • Enable network sharing.
  • Reconnect the disinfected computer or local network to the Internet.

CAUTION Due to the "Email-Worm." detection prefix, F-Secure Anti-Virus will automatically suggest deletion of the infected files. DO NOT select the "Delete" option however, as this worm includes a viral component and the files it infects should be disinfected rather than deleted. At the same time, the worm's dropper and downloader files should be deleted from a computer to prevent its re-infection. See the names of the dropper and downloader files in the Details section.

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

Luder is an email worm, a dropper for a trojan downloader and a file infector. The worm sends itself as attachment named 'postcard.exe' (or similar) in email messages with the 'Happy New Year!' subject (or similar). The trojan downloader downloads and runs files from a website.


After the worm's file is run, it copies itself to Windows System folder with the name ppl.exe.The worm also drops a trojan downloader file with a random name into the Windows System folder and starts it.


Before spreading, the worm collects email addresses from an infected computer. It locates and reads the WAB (Windows Address Book) file. The worm sends messages with the following characteristics:

  • Subject:Happy New Year!
  • Attachment:postcard.exe

Later variants of the worm use different Subject fields and Attachment names.The worm avoids sending emails to email addresses that contain any of the following:

  • microsoft
  • .mil
  • .gov


The worm scans all fixed and remote drives starting from Z: to C: and looks for files with the following extensions:

  • hta
  • txt
  • htm
  • exe
  • scr
  • rar

The worm collects additional email addresses to spread to files with .hta, .txt and .htm extensions.The files with .scr and .exe extensions get infected. For every executable file found, the worm creates a copy with a random name and a .t extension. Then it tries to infect the files, if they are in PE (Portable Executable) format. The worm inserts a small piece of code into the victim files and then redirects the entry point to that address. This small piece of code starts the worm's copy (randomly named file with .t extension) and then passes control to the host file.It should be noted that the worm is quite buggy and can corrupt files upon infection. Files with .rar extension are not affected, but the worm's author probably plans to process them in future versions of his malware. The worm also does not infect files protected by Windows Safe File Check.The worm terminates processes with the following substrings in their names:

  • anti
  • viru
  • troja
  • avp
  • nav
  • rav
  • reged
  • nod32
  • spybot
  • zonea
  • vsmon
  • avg
  • blackice
  • firewall
  • msconfig
  • lockdown
  • f-pro
  • hijack
  • taskmgr
  • mcafee

In addition the worm closes the Registry Editor's window.

Registry Modifications

Creates these keys:

  • [HKCU\Software\Microsoft\Windows\CurrentVersion\Run] "agent" = "%WinSysDir%\ppl.exe"
  • [HKLM\Software\Microsoft\Windows\CurrentVersion\Run] "agent" = "%WinSysDir%\ppl.exe"

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