Now recognizing what could be a virus may reduce your risk. It however doesn't eliminate it. Getting something from someone that posts on UseNet on a regular bases doesn't clear them of being a virus spreader. They may be doing it intentionally or unintentionally. Maybe someone is ghosting the author who is known for posting to that group. Maybe the regular poster is infected and is not aware of the virus or can't stop their computer from doing what it is doing. So lurk and be patient before downloading and most defiantly wait before executing any programs or files that you get. And eventually you'll become so Internet savvy that this becomes second nature to you.
So pay attention to these factors: does the posted article follow that groups format, size of posted articles, author ghost-name, authors ISP IP address, Header information, file extensions, and other authors that are not posting files but messages. Because they will tell you what author is spreading viruses or trolling. As a community you must function to eliminate these delinquent people. So if a virus hits you, try clearing it as soon as possible or going somewhere's and posting a warning about that author or his post. But remember, that other author is the last consider factor into determining a virus or not. As it could be a troll trying to discredit someone because of what that author said to them in another group.
This all boils down to your judgment call on downloading and executing which files. The best way to avoid viruses is to not download files.
FAQ answers attributed to Raymond E. Feist are copyright by Raymond E. Feist.
It should also be born in mind that the answer given was only applicable on the date written, and to a specific question. You may find further, similar questions, in the FAQ.