Anti virus.

[Vampiroth]

Kaspersky.

[RadmaKanow]

I don't know much about AVs but I gave Norton Internet Security and I feel safe. Runs in the background all the time and I haven't noticed any system performance issues. Plus it protects me in real time. Example, 2 days ago, half an hour of browsing I had almost constant AV notification: hack attempt from <ip here> blocked, no user reaction needed. And it runs complete and full system scans while I'll go afk. Automatically. And stops it when I start using PC again.

Overall, it protects me all the time and check system when it won't interfere with anything.

[Lilbruz]

If you dont want to have an antivirus/firewall running in the background, thats your choice.

However, you need to understand that scanning once a week (and having it turned off other than that) is a risky thing to do for most people. If you know what you are doing online, and know what to avoid, I would argue that you wouldnt even need any protection software. This is however NOT the case for the large majority of people.

If you are worried your PC cant handle something running in the background, maybe you either need to upgrade your PC or try some of the new software. As others have said, with modern computers, the power needed to run antivirus/firewall is very low (depending on the software ofc) compared to other things you have running.

You also need to understand that virus and malware is something you need proactive defense against as a general rule, so starting your virus software and running it once a week is not the way to do that. There are thousands of new virus and malware made and changed every single day, so your monday update is more or less already too old come tuesday. The best antivirus software updates daily (you can set it to weekly or something if you like, but it would be silly if you ask me), but having something that monitors your traffic is still the best way of protecting yourself if you dont count unplugging the cable.

That being said, I have run Kaspersky for a few years, and its in no way cheap, but it has the features I like, and its running smooth, and I never had a single problem with it. I tend to go for a paid option myself, as my mindset is that "you get what you pay for", and while free solutions can be just fine, I just dont want to save money on something like this.

Also, I have also suggested Microsoft Security Essentials for lots of people, and if I re-install peoples PC´s (I work IT), I usually just install MSE as well so they have at least a form of protection.

My 2 cents

[zaïchï]

I don't know much about AVs but I gave Norton Internet Security and I feel safe.

i would use norton if it was free cos it used to be awsome ( windows 1.11 3.1 95 98 se ) then it was sloppy ( 2000 to vista ) but it has been improffed but i still prefere avast over it + the free version is LOADS cheaper than norton

[kidsafe]

Everything Notarget said is true, so I thought I would expand on why I settled on Comodo. I tried BitDefender, Kaspersky, Panda Cloud, Avira, F-Secure, Norton, Security Essentials and Comodo in the past year.

* All of them except MS Security Essentials provide some sort of zero-day protection, so I was able to drop it out of the running immediately.

* BitDefender, Kaspersky and F-Secure all seem to constantly write between 10-30KB/s to my HDD. This would not be an issue, but I can hear the head of the HDD ticking away. It's annoying because I have a very silent machine otherwise. Norton and Avira also do this to a smaller extent, but under 10KB/s writes. Still annoying.

* Cost. Comodo is free. Panda Cloud is free. I heard BitDefender Cloud Free is coming out soon. There's a free version of Avira. Everything else requires a subscription. Out of all of these, the free versions of Comodo and Panda are the only ones with what I consider a complete list of AV functionality.

* Usability. I like Comodo's multitude of options and layout. BitDefender, Kaspersky, Panda, Norton are fine as well. F-Secure and Avira have draconian UIs. This is not a problem for me, but for novice users a lot of the pop-up warnings and procedures are ambiguous at best.

* Extra features. BitDefender, Comodo, Norton, etc. all come with firewalls. Comodo's seems to have the most advanced options for defining your own rules. Comodo is the only suite that offers a sandbox for allowing unknown applications to run without risking the rest of the system.