SSL VPN hack vulnerability details to emerge

Black Hat demo to show even extended validation certificates are vulnerable to man-in-the-middle attacks

Confidential online connections like banking transactions made from public wireless hotspots remain vulnerable to attacks despite improved security that was supposed to fix the problem, researchers will demonstrate at the Black Hat security conference.

The vulnerability means that attackers can lurk in the middle of what victims think are secure SSL sessions with banks, retailers and other secure Web sites, picking off passwords and other information that can be used later to steal account funds or compromise confidential business data, say the researchers, Mark Zusman, a consultant with Intrepidus, and Alexander Sotirov, an independent researcher.

An improved method of qualifying businesses for SSL certificates - called extended validation (EV) SSL turns the address bar in browsers green to assure users that the connection is in fact being made using EV SSL certificates. It is supposed to indicate that end users are connecting with a legitimate business, not an attacker. To do so, the entity obtaining the SSL certificate has undergone prescribed scrutiny and qualified for the certificate.

But a green bar may hide the fact that the browser is actually connecting using SSL certificates approved via the traditional, less secure version of certificate issuance called domain validation (DV), which has no guarantee that such validation criteria were met, Zusman says. Those DV connections can be compromised by attackers.

Fixing the vulnerability is complex and would require all Web sites to conform, so the best defense is to avoid using insecure public Wi-Fi networks, he says. "Use EVDO [broadband wireless service] or some other mobile broadband service that makes it more difficult to execute this type of attack," he says. "Keep yourself out of situations where attackers can get at you."To take advantage of this weakness, hackers would set up laptops in a public Wi-Fi zone and use well known methods for compromising the wireless access points such as ARP or DNS spoofing or hacking management platforms.

With control of the DNS for the access point, the attackers can establish their machines as men-in-the-middle, monitoring what victims logged into the access point are up to. They can let victims connect to EV SSL sites - turning the address bars green. Subsequently, they can redirect the connection to a DV SSL sessions under a certificates they have gotten illicitly, but the browser will still show the green bar.

"The scary part is that from the victim's side there's really no sign that anything went wrong unless they look at the EV SSL session on the certificate that is served," Zusman says, which is something most users don't do." After the fact they may see that someone accessed their account, but during the attack it's very difficult to detect."

Attackers could drop malware into victims' browsers that would grab passwords later when they access sensitive sites from secure networks that the attackers have not cracked, he says.

Many Web sites are hybrid in that EV SSL is required to log in, but elements of the pages are protected by DV SSL certificates. One example is Google Analytics service doesn't require EV SSL to access customer data, but that data could be part of a Web page that does require EV SSL certificates for entry.

"The fix requires pretty basic changes to the way browsers deal with EV certs," Sotirov says. If elements of the page use DV SSL certs, the browser would not display them, he says, which could break Web sites from the user's perspective. "It wouldn't invalidate the entire site just that part with content from third-party, non-EV SSL servers."

Web sites can fix the problem by adopting all EV SSL certs for all the elements of their sites, even those served by third parties. Bu that would require creators of Web sites to find out whether all the elements of their pages use EV SSL certificates. "It is not an upgrade process [Web designers] would likely go through. The Web is not good at these upgrades," Satirov says.

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 black hatssl vpn

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

Tim Greene

Network World
Show Comments

Father’s Day Gift Guide

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

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.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?