A new UPX packed variant of MyDoom worm - Mydoom.Q, was found on August 3rd, 2004. The worm spreads like its previous variants and it also uses Yahoo People Search to search for more victims' email addresses.
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The worm's file is a PE executable 21504 bytes long packed with UPX file compressor. The unpacked worm's size is about 62 kilobytes.
After the worm's file is run, it opens Notepad application. Then the worm copies itself as WINLIBS.EXE file to Windows System directory and creates a startup key for the copied file in Windows Registry:
where %WinSysDir% represents Windows System folder. As a result, the worm's file is started every time Windows starts.
Additionally the worm creates the following Registry key:
The worm creates a mutex named 'NorthernLightMixed'.
The worm spreads in emails. Before spreading it collects email addresses from an infected computer. The worm reads Windows Address Book file, reads files in Temporary Internet Files folders and Windows System folder. Files with the following extensions are checked:
Additionally the worm can connect to 'email.people.yahoo.com' server and tries to search for victims' email addresses there.
The worm doesn't send itself to email addresses that contain any of the following substrings:
The worm spreads in emails with different subject and body texts and with different attachment names. The subject line is selected from the following variants:
The message body can contain user name, domain name and the following text strings:
The attachment name is selected from the following variants:
The attachment extension is selected from these variants:
Also the worm can send itself inside a ZIP archive.
The worm fakes the sender's email address. It uses the following user names for the fake email address:
In the very beginning of its execution the worm creates a thread that enumerates processes and terminates the ones that have the following substrings in their names: