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Verisign says new gTLDs put millions at risk

Kevin Murphy, May 26, 2016, Domain Tech

Verisign has revived its old name collisions security scare story, publishing this week a weighty research paper claiming millions are at risk of man-in-the-middle attacks.
It’s actually a study into how a well-known type of attack, first documented in the 1990s, might become easier due to the expansion of the DNS at the top level.
According to the paper there might be as many as 238,000 instances per day of query traffic intended for private networks leaking to the public DNS, where attackers could potentially exploit it to all manner of genuinely nasty things.
But Verisign has seen no evidence of the vulnerability being used by bad guys yet and it might not be as scary as it first appears.
You can read the paper here (pdf), but I’ll attempt to summarize.
The problem concerns a virtually ubiquitous protocol called WPAD, for Web Proxy Auto-Discovery.
It’s used by mostly by Windows clients to automatically download a web proxy configuration file that tells their browser how to connect to the web.
Organizations host these files on their local networks. The WPAD protocol tries to find the file using DHCP first, but fails over to DNS.
So, your browser might look for a wpad.dat file on, depending on what domain your computer belongs to, using DNS.
The vulnerability arises because companies often use previously undelegated TLDs — such as .prod or .global — on their internal networks. Their PCs could belong to domains ending in .corp, even though .corp isn’t real TLD in the DNS root.
When these devices are roaming outside of their local network, they will still attempt to use the DNS to find their WPAD file. And if the TLD their company uses internally has actually been delegated by ICANN, their WPAD requests “leak” to registry or registrant.
A malicious attacker could register a domain name in a TLD that matches the domain the target company uses internally, allowing him to intercept and respond to the WPAD request and setting himself up as the roaming laptop’s web proxy.
That would basically allow the attacker to do pretty much whatever he wanted to the victim’s browsing experience.
Verisign says it saw 20 million WPAD leaks hit its two root servers every single day when it collected its data, and estimates that 6.6 million users are affected.
The paper says that of the 738 new gTLDs it looked at, 65.7% of them saw some degree of WPAD query leakage.
The ones with the most leaks, in order, were .global, .ads, .group, .network, .dev, .office, .prod, .hsbc, .win, .world, .one, .sap and .site.
It’s potentially quite scary, but there are some mitigating factors.
First, the problem is not limited to new gTLDs.
Yesterday I talked to Matt Larson, ICANN’s new vice president of research (who held the same post at Verisign’s until a few years ago).
He said ICANN has seen the same problem with .int, which was delegated in 1988. ICANN runs one of .int’s authoritative name servers.
“We did a really quick look at 24 hours of traffic and saw a million and a half queries for domain names of the form, and that’s just one name server out of several in a 24-hour period,” he said.
“This is not a new problem, and it’s not a problem that’s specific to new gTLDs,” he said.
According to Verisign’s paper, only 2.3% of the WPAD query leaks hitting its root servers were related to new gTLDs. That’s about 238,000 queries every day.
With such a small percentage, you might wonder why new gTLDs are being highlighted as a problem.
I think it’s because organizations typically won’t own the new gTLD domain name that matches their internal domain, something that would eliminate the risk of an attacker exploiting a leak.
Verisign’s report also has limited visibility into the actual degree of risk organizations are experiencing today.
Its research methodology by necessity was limited to observing leaked WPAD queries hitting its two root servers before the new gTLDs in question were delegated.
The company only collected relevant NXDOMAIN traffic to its two root servers — DNS queries with answers typically get resolved closer to the user in the DNS hierarchy — so it has no visibility to whether the same level of leaks happen post-delegation.
Well aware of the name collisions problem, largely due to Verisign’s 11th-hour epiphany on the subject, ICANN forces all new gTLD registries to wildcard their zones for 90 days after they go live.
All collision names are pointed to, a reserved IP address picked in order to catch the attention of network administrators (DNS uses TCP/IP port 53).
Potentially, at-risk organizations could have fixed their collision problems shortly after the colliding gTLD was delegated, reducing the global impact of the vulnerability.
There’s no good data showing how many networks were reconfigured due to name collisions in the new gTLD program, but some anecdotal evidence of admins telling Google to go fuck itself when .prod got delegated.
A December 2015 report from JAS Advisors, which came up with the idea, said the effects of name collisions have been rather limited.
ICANN’s Larson echoed the advice put out by security watchdog US-CERT this week, which among other things urges admins to use proper domain names that they actually control on their internal networks.