I'd like to know if the following is enough to avert malware as I feel that the press and other advisory resources aren't always precisely clear on all the methods as to how PCs get infected.
To my mind, the key step to getting infected is a conscious choice by the user to run an executable attachment from an email or download, but also viewing content that requires a plug-in (Flash, Java or something else). This conscious step breaks down into the following possibilities:
don't open email attachments: certainly agree with this. But lets try to be clear: email comes in 2 parts -the text and the attachment. Just reading the email should not be risky, right? But opening (i.e. running) email attachments IS risky (malware can be present in the attachment)
don't execute downloads (e.g. from sites linked from in suspect emails or otherwise): again certainly agree with this (malware can be present in the executable). Usually the user has to voluntary click to download, or at least click to run the executable. Question: has there ever been a case where a user has visited a site and a download has completed on its own and run on its own?
don't run content requiring plug-ins: certainly agree: malware can be present in the executable. I vaguely recall cases with Flash but know of the Java-based vulnerabilities much better.
Now, is the above enough? Note that I'm much more cautious than this. What I'm concerned about is that the media is not always very clear about how the malware infection occurs. They talk of "booby-trapped sites", "browser attacks" - HOW exactly?
An accepted answer would fill in any holes I've missed here so we have a complete general view of what the threats are (even though the actual specific details of new threats vary, but the general vectors are known).