The worm now uses USB sticks to spread. By copying itself in a random folder created inside the RECYCLER directory - used by the Recycle Bin to store deleted files - and creating an autorun.inf file in the root folder of the drive, the worm automatically executes if the Autorun feature is enabled.
The worm also patched certain TCP functions to block access to security-related websites by filtering every address that contains certain strings. This makes it harder to remove since information about it is nearly impossible to gather from an infected computer. Additionally, it removes all access rights of the user, except execute and directory usage, to protect its files.
The worm is also built to avoid antivirus detection by working with rarely used application programming interfaces (APIs) in order to avoid virtualisation technologies. It disables Windows updates and certain network traffic, optimising itself for Vista features to help its spread.
Win32.Worm.Downadup.B also comes with a domain name generation algorithm similar to the one found in botnets like Rustock. It composes 250 domains every day and checks for updates or other files to download and install.
Possessing a state-of- the-art update system, a good protection scheme and many people who don’t patch their systems, this worm has damaging potential to become as dangerous as already established botnets like Storm or Srizbi, according to BitDefender.