On the heels of my post on Microsoft's SIRv4 earlier this week, reader Ray posed a great question that elicited some nuanced responses from fellow handlers Mark H and Swa F. All parties have agreed to allow me to share the conversation with the ISC readership.

From Ray:

What is, "up to date anti-virus software"?  Is there a de facto standard of how often or what defines when a system is up to date or not up to date?  My goal isn't to split hairs.  There are a lot of moving pieces (in the background) to this question & where I work.  I would like to know what other organizations use; besides sooner is better. 

Mark H's response:

To me the definition of up to date is the latest pattern file for that particular application.  So I tend to configure AV products to check at least hourly for updates and apply them.  Some product interestingly however still consider daily or weekly to be ok.  Putting on my QSA hat usually I accept daily updates as being ok (assuming that the AV product is therefore at the lates pattern update), go beyond that and you'd best have a very good reason for lagging.

Ray's reply:

While wearing the AV hat at my last company I expected a drop in infections when I stabilized our (pattern file) distributions, but didn't expect such a dramatic drop in the rate.  With three updates a day I hit < .5% systems were more than one day out of date.  Since moving to a different company with different responsibilities I see one update a day and a 5 day window for updates with the target of only 90% of systems updated I see...room for improvement but face a mind set challenge.  I was curious what other "standards" were.

Swa's feedback:

Agreement with Mark: hourly is THE way to go. 

Photo courtesy of nukeitfromorbit.com 

Great discussion, Ray and handlers. Thanks for letting us share.

Russ McRee | @holisticinfosec