Posted by MOBster (62.254.0.4) on March 20, 2001 at 17:17:25:
Technical description:
When the worm attachment is executed, the Wsock32.dll file is modified or replaced. Once the worm has infected wsock32.dll, it has the abilty to monitor the Internet connection as well as incoming and outgoing email traffic. The worm then scans for email addresses. When an email address is detected whether on an Internet site or in email being sent or received, the worm waits for a period of time and then sends an infected message to the detected address.
The worm attempts to connect to the alt.comp.virus newsgroup. If it connects successfully, then the worm uploads its own plug-ins to this newsgroup in an encrypted form. It goes thru the subject header of the messages, and tries to match a specific format. The subject header will also specify the version number of the attached plug-in if the plug-ins are present. If newer versions of the plug-ins are found, the worm downloads them and updates its behavior.
One of the plug-ins for W95.Hybris.gen generates a spiral image. Upon execution, the plug-in initially loads OpenGL libraries which are used to draw a large black and white spiral image. It also registers itself as a service; this prevents it from being displayed in the Close Programs dialog box. For additional information on this, see the document W95.Hybris.plugin.
This worm also has a plug-in that infects executable programs. The DOS EXE infection is fairly simple dropping technique. The virus code is appended to the end of the file with a small 16-bit dropper routine. This routine creates a temporary file with an .exe extension in the TEMP folder and executes it. It then deletes the temporary executable. In this way, Wsock32.dll is infected with the actual worm body. The PE executables have a much more complicated file infection process. PE files become infected only if they have a long enough code section. The virus infection plug-in packs the original code area and overwrites it if it will fit in the same place. This complicated antiheuristic infection technique is difficult but possible to repair.
If Wsock32.dll is being used by the system, the worm cannot modify it. In this situation, the worm will add a registry entry to one of the following subkeys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\RunOnce
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
It always alternates between these two keys as the worm spreads from one computer to another. The worm hooks onto the following exports of Wsock32.dll:
send()
recv()
connect()
Whenever you send email, the worm sends a second message to the same person, attaching a copy of itself using a randomly generated file name.
If you don't know whats in it - then bin it !!!
Best Wishes,
MOB