The VBS.Netlog worm is a good example (although harmless) of a virus/worm that can invade your system while online. Another virus that gained wide spread fame was the 911 Virus that invaded systems, formatted the hard drives (destroying any data on them) and even dialed 911 through the modem. Both of these worms or viruses spread through the Internet not via email but through accessible shared drives on computer connected to the Internet even on dial-up.
Apart from getting the latest version of anti virus there are copuple of online solutions. Of which one is free online virus scan. Here are couple of option you can use.
1. No Virus Thanks: If you have a suspicious file you can submit it in the form below and our system will analyze your file with 24 AntiVirus Engines and will report back the analysis result.
2. A similar alternative is provided by kaspersky. Only one file of up to 1 MB can be checked at any one time.
3. Trend Micro™ HouseCall is an application for checking whether your computer has been infected by viruses, spyware, or other malware. HouseCall performs additional security checks to identify and fix vulnerabilities to prevent reinfection.
Hope these can come handly.. If you have some more tools please do share..