After reading
@Cowpipe 's last post, I think there's no need for antivirus on my PC since I can't stop NSA's spying anyways
misconception from you; you don't need an AV for stopping the NSA, you need it to stop malwares.
if you aren't an terrorist or anti-gov virulent activist , you don't have to worry , NSA has better things to do than spying you.
how NSA works:
1- NSA implement several proxies/servers around the worlds mostly at the entrance/exit of ISP providers cables.
2- on those proxies/servers, they setup powerful filtering programs, traffic monitors and data analyzers
3- on those programs they register algorithm managing key words combinations and strings like "bin laden" , "revenge", "attack" , "bomb", "USA"
4- the algorithm then evaluate millions of input from the various internet users to specifically look for those strings.
5- once a string composed of several keywords is identified, the program notify the NSA operator for a suspicious activity from that user.
6- then the operator will use various methods to start analyzing the activity of that particular individual, to check his "threat potential"
7- if the user is known or reveal to be potentially dangerous , an deeper approach is taken, hacking the user computer, mail, watching his online activity in real time
8- if the user is solitary, the case is relayed to local agencies (FBI, etc...), if he is part of a group , the spying is extended until all participants are located and evidences stored.