Microsoft correctly predicts reliable exploits just 27% of the time

Exploitability index ratings useless, experts argue; Microsoft disagrees

Microsoft's monthly predictions about whether hackers will create reliable exploit code for its bugs were right only about a quarter of the time in the first half of 2009, the company acknowledged Monday.

"That's not as good as a coin toss," said Andrew Storms, director of security operations at nCircle Network Security. "So what's the point?"

In October 2008, Microsoft added an "Exploitability Index" to the security bulletins it issues each month. The index rates bugs on a scale from 1 to 3, with 1 indicating that consistently-successful exploit code was likely in the next 30 days, and 3 meaning that working exploit code was unlikely during that same period.

The idea was to give customers more information to decide which vulnerabilities should be patched first. Before the introduction of the index, Microsoft only offered impact ratings -- "critical," "important," "moderate" and "low" -- as an aid for users puzzled by which flaws should be fixed immediately and which could be set aside for the moment.

But in the first half of this year, Microsoft correctly predicted exploits just slightly more than one out of every four times.

"Forty-one vulnerabilities were assigned an Exploitability Index rating of 1, meaning that they were considered the most likely to be exploited within 30 days of the associated security bulletin's release," Microsoft stated in its bi-annual security intelligence report , which it published Monday. "Of these, 11 were, in fact, exploited within 30 days."

That means Microsoft got it right about 27% of the time.

Microsoft also tallied its predictions by security bulletins -- in many cases a single bulletin included patches for multiple vulnerabilities -- to come up with a better batting average. "Sixteen bulletins received a severity rating of Critical," it said in its report. "Of these, 11 were assigned an Exploitability Index rating of 1. Five of these 11 bulletins addressed vulnerabilities that were publicly exploited within 30 days, for an aggregate false positive rate of 55%."

The company defended its poor showing -- even on a bulletin-by-bulletin level it accurately predicted exploitability only 45% of the time -- by saying it was playing it safe. "The higher false positive rate for Critical security bulletins can be attributed to the conservative approach used during the assessment process to ensure the highest degree of customer protection for the most severe class of issues," said Microsoft.

"There's some validity to that," agreed Storms. "They're going to err on the side of caution, if only to prevent people saying 'I told you so' if an exploit appears later."

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags Microsoft

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.
Gregg Keizer

Gregg Keizer

Computerworld (US)
Show Comments

Cool Tech

Toys for Boys

Family Friendly

Stocking Stuffer

SmartLens - Clip on Phone Camera Lens Set of 3

Learn more >

Christmas Gift Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Aysha Strobbe

Microsoft Office 365/HP Spectre x360

Microsoft Office continues to make a student’s life that little bit easier by offering reliable, easy to use, time-saving functionality, while continuing to develop new features that further enhance what is already a formidable collection of applications

Michael Hargreaves

Microsoft Office 365/Dell XPS 15 2-in-1

I’d recommend a Dell XPS 15 2-in-1 and the new Windows 10 to anyone who needs to get serious work done (before you kick back on your couch with your favourite Netflix show.)

Maryellen Rose George

Brother PT-P750W

It’s useful for office tasks as well as pragmatic labelling of equipment and storage – just don’t get too excited and label everything in sight!

Cathy Giles

Brother MFC-L8900CDW

The Brother MFC-L8900CDW is an absolute stand out. I struggle to fault it.

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?