Microsoft’s next major release of Internet Explorer (IE) will support an internet standard that allows web servers to force browsers to make a secured connection when the site supports encryption.
Microsoft has confirmed IE 12 will support HTTP Strict Transport Security (HSTS), a standard ratified in 2012 by the Internet Engineering Task Force (IETF), which is currently implemented in all major browser except for IE.
HSTS allows a web server to issue a HTTP response header that sets a policy in supported browsers so that it always requests a certain domain over Secure Sockets Layer (SSL) encryption.
Microsoft notes on its new status page for modern.ie (where web developers can test their site against IE 6 to 11) that HSTS is “in development” and will reduce the surface area for man-in-the-middle attacks.
The move will bring IE up to par with Chrome and Firefox, which supported HSTS as far back as 2009. The two browsers supported the standard before security researcher Moxie Marlinspike in 2009 released “SSLstripper”, a man-in-the-middle attack tool that stripped SSL from HTTPS websites without triggering the usual warnings that browsers offered for suspicious connections.
As Marlinspike noted, the tool “will transparently hijack HTTP traffic on a network, watch for HTTPS links and redirects, then map those links into either look-alike HTTP links or homograph-similar HTTPS links.” The tool can also spoof the ‘favicon’ padlock in browsers that indicates when a connection is SSL encrypted.
One scenario HSTS can be useful is on free public wifi networks where an attacker can intercept web traffic by tricking a device on the network into treating the attacker’s device as the wifi router. Without HSTS policy being enforced, attackers could gain the login credentials for sites that should otherwise be protected by a HTTPS connection.
While Microsoft’s support in IE for the standard has come relatively late, it could have a positive impact on the adoption of encryption technologies by website operators.
According to Electronic Frontiers Foundation (EFF) technologist Jeremy Gillula, most websites don’t support the strict HTTPS standard. Sites that do include some Google domains, Dropbox, Twitter, Microsoft’s SkyDrive and the UK Government’s website. Yahoo also announced as part of its ongoing website encryption plans that it will be implementing HSTS within the next few months.
“So why haven't more websites enabled HSTS? The biggest reason, we fear, is that web developers just don't know about it. Another problem is that support for HSTS in browsers has been incomplete: only Chrome, Firefox, and Opera have had HSTS support for a significant period,” said Gillula.
“This is changing though: we noticed that Apple quietly added HSTS support to Safari in OS X 10.9. For now, Internet Explorer doesn't support HSTS—which means that there's basically no such thing as a secure website in IE.”
HSTS is one of five security measures the EFF has been campaigning for website operators to implement following leaks by former National Security Agency contractor Edward Snowden. The measures include encrypting data centre links, as well as support for HTTPS, HSTS, forward secrecy, and STARTTLS.
This article is brought to you by Enex TestLab, content directors for CSO Australia.