[ams6110]

In the past, on Windows and Macs (pre-OSX), it was pretty much a requirement unless your machine was really stand-alone and you never dealt with files from any untrusted sources.

These days, if you keep your system patched, use an unprivileged account for your normal activity, use a local firewall and/or NAT, and stay away from shady websites you are probably pretty safe.

I have similar experiences with a friend who's constantly getting malware even though he's running Windows 7 and Microsoft Security Essentials. The main vector seems to be PDF files; he deals with a lot of them via email as part of his job, and he's very much in the habit of just opening PDFs in email before he even really looks at who the sender is.

I agree that many AV programs slow the sytem way down, and in general cause problems, and don't seem to really guarantee that you won't get infected. And FUD is a huge part of how it's marketed. Even Windows itself will nag you with ominous warnings if you don't have any AV software installed.

[jiggy2011]

There is possibly a problem with user education here.

Running software on your computer that is not set to automatically pull down and install security patches to me seems like a far bigger problem than not running AV software. Windows does warn you if you turn automatic updates off , but afaik there is rarely such a warning about third party software.

In your friends case it would seem that he is not getting updates from adobe, since viewing a PDF file should not cause third party code execution so he must be getting PDFs that are exploiting his PDF reader (presumably adobe fixes these quickly as they arise).