The best defense humans have against viruses is their immune system. Innate immunity defends aginst pathogens in a nonspecific manner. Innate responses to viruses include inflammation, sneezing, and destroying infected cells.

Adaptive immunity defends against specific pathogens. After the initial infection, the body will produce antibodies to target a specific pathogen, a virus in this example. These antibodies will allow the body to respond more rapidly to future invasions. Vaccination is an example of adaptive immunity. They work by presenting the immune system with antigen(s), which stimulates the production of antibodies.

I would like to note that antibiotics are ineffective against viruses (such as the common cold). Antibiotics are for bacterial infections. Antiviral drugs are what you would take for viral infections.