I tried to search about this virus in avast virus database but it did not result in any positive matches,does that mean even my computer is vulnerable?
and yes i have the latest version of virus database.
Since there is no standard for naming new viruses, a simple search for that name might not reveal any hit, but avast might call it something different, that is why you also need to find aliases, a search for that virus name may reveal information about it and also give aliases. These aliases could be checked against the virus database.
However, this particular virus/worm doesn't matter, it could be any new virus that hasn't yet been added, a so called Day 0 (Zero) virus and you can also protect yourself from those by taking precautions to limit their effect. Multi-Application/Level approach to security, ensure your OS, firewall and security programs are up to date, etc.
You might also consider proactive protection, in order to place files in the system folders and create registry entries you need permission. Prevention is much better and theoretically easier than cure.
Whilst browsing or collecting email, etc. if you get infected then the malware by default inherits the same permissions that you have for your user account. So if the user account has administrator rights, the malware has administrator rights and can reap havoc. With limited rights the malware can't put files in the system folders, create registry entries, etc. This greatly reduces the potential harm that can be done by an undetected or first day virus, etc.
Check out the link to DropMyRights (in my signature below) - Browsing the Web and Reading E-mail Safely as an Administrator. This obviously applies to those NT based OSes that have administrator settings, winNT, win2k, winXP.