Yeah, as others have said definition updates will be dependent on your specific antivirus application. There's not a universal database or anything AFAIK
I also use avira from some pcs....but it has not been updated since last 2 months...the update always fails.....can you tell me how can i manually update it or from where can i find the update file???
You will never get the anti virus up to date. Each anti virus has its updates every month which includes scripts for new viruses found, if you dont update that software , it is of no use. The people who design these viruses study the new anti virus and then design the virus that will harm your computer. You can call this as a reverse engineering.
I use Mc Afee and NOD ESET 32 anti-virus on my personal computer. NOD ESET 32 can always detect if there's a malicious software or worm crawling when I'm attempting to open an odd downloadable program while Mc Afee scans my internal files to check if my computer is infected or not.
SSLuser, you may need to reinstall. I do not have that problem and mine updates everyday. Try uninstalling, downloading the newest version and installing fresh
I use QuickHeal antivirus. It gets updated as soon as the recent update is available. It gets updated automatically when the machine is online or connected to internet. I really like QuiclHeal antivirus.
One of the great antivirus software is NOD32 antivirus system by eset. It has helped in finding numerous viruses which some of the other antivirus programs failed to find out. I tested it for few systems and later on became a great fan of it. I recommend it a lot.