Don't download anything and everything you encounter.
I haven't used antivirual software in years, by way of careful file checks. You can always check a file for malicious wares, or simply never download anything. File legitimacy is never guaranteed, but only using trusted sources can increase your safety as well.
There are also pseudo-spychecking methods one can use cheaply [or cheaper than Spyware], and these are as simple as using a two-state HDD system, wherein you use a small HDD to download the file/program, confirm it's legitimacy, and continue to carry it over to a main storage. Alternatively, one can ask a trusted Pi---Er... An experienced computer geek [Like those of us here] on what's safe and what isn't. Real, literal, and actual software Pir--- /./COUGH././ computer geeks like me don't spread our digitally-transmitted diseases like the fake-outs do. We believe software and information should be shared freely, but safely, thus furthering the net's safety when our advice is taken into consideration.
As a final note, I'd like to point out that just deleting the file is not always enough. Unless you have HDD over-writers, the information is still technically on your HDD until it is written over by higher-priority data. If you want to confirm your data security, one recommendation is to delete the viral infection, then over-write it manually by crating an exuberant amount of dummy files [either massive text-based files, like a huge Rich Text Format with just a bunch of copy/pasta, millions of characters in length, or massive blank .PNG files], copy and paste them in a folder, and copy/paste those folders until you've basically taken up your entire HDD with blank files. o_o;
This way, the "deleted" Viral infection can't work it's way back into your main system when left to bide.
