There are common signs of infected computers.
1. Your computer runs consistently slowly than normal.
2. Locks up or stops responding.
3. When you connect to the Internet, all types of windows open or display pages you have not requested.
4. Programs don’t work properly
5. You start getting popups telling you to download a program.
You might be infected but some of this signs could also indicate hardware or software problems that have nothing to do with a virus.
While there is no method that can 100% guarantee that your computer will be not be infected, there are a number of steps that you can take to lessen the probability of this happening.
1. Install antivirus and antispyware programs from a trusted source
2. Don't open files on your drive that you're not expecting
3. Update software regularly
4. Use strong passwords and keep them secret
5. Never turn off your firewall
6. Use flash drives cautiously, but don’t put an unknown flash (or thumb) drive into your computer.