Login
Virtual private networking (VPN) companies market their services as a way to prevent anyone from snooping on your Internet usage. But new research suggests this is a dangerous assumption when connecting to a VPN via an untrusted network, because attackers on the same network could force a target’s traffic off of the protection provided by their VPN without triggering any alerts to the user.
Image: Shutterstock.
When a device initially tries to connect to a network, it broadcasts a message to the entire local network stating that it is requesting an Internet address. Normally, the only system on the network that notices this request and replies is the router responsible for managing the network to which the user is trying to connect.
The machine on a network responsible for fielding these requests is called a Dynamic Host Configuration Protocol (DHCP) server, which will issue time-based leases for IP addresses. The DHCP server also takes care of setting a specific local address — known as an Internet gateway — that all connecting systems will use as a primary route to the Web.
VPNs work by creating a virtual network interface that serves as an encrypted tunnel for communications. But researchers at Leviathan Security say they’ve discovered it’s possible to abuse an obscure feature built into the DHCP standard so that other users on the local network are forced to connect to a rogue DHCP server.
“Our technique is to run a DHCP server on the same network as a targeted VPN user and to also set our DHCP configuration to use itself as a gateway,” Leviathan researchers Lizzie Moratti and Dani Cronce wrote. “When the traffic hits our gateway, we use traffic forwarding rules on the DHCP server to pass traffic through to a legitimate gateway while we snoop on it.”
The feature being abused here is known as DHCP option 121, and it allows a DHCP server to set a route on the VPN user’s system that is more specific than those used by most VPNs. Abusing this option, Leviathan found, effectively gives an attacker on the local network the ability to set up routing rules that have a higher priority than the routes for the virtual network interface that the target’s VPN creates.
“Pushing a route also means that the network traffic will be sent over the same interface as the DHCP server instead of the virtual network interface,” the Leviathan researchers said. “This is intended functionality that isn’t clearly stated in the RFC [standard]. Therefore, for the routes we push, it is never encrypted by the VPN’s virtual interface but instead transmitted by the network interface that is talking to the DHCP server. As an attacker, we can select which IP addresses go over the tunnel and which addresses go over the network interface talking to our DHCP server.”
Leviathan found they could force VPNs on the local network that already had a connection to arbitrarily request a new one. In this well-documented tactic, known as a DHCP starvation attack, an attacker floods the DHCP server with requests that consume all available IP addresses that can be allocated. Once the network’s legitimate DHCP server is completely tied up, the attacker can then have their rogue DHCP server respond to all pending requests.
“This technique can also be used against an already established VPN connection once the VPN user’s host needs to renew a lease from our DHCP server,” the researchers wrote. “We can artificially create that scenario by setting a short lease time in the DHCP lease, so the user updates their routing table more frequently. In addition, the VPN control channel is still intact because it already uses the physical interface for its communication. In our testing, the VPN always continued to report as connected, and the kill switch was never engaged to drop our VPN connection.”
The researchers say their methods could be used by an attacker who compromises a DHCP server or wireless access point, or by a rogue network administrator who owns the infrastructure themselves and maliciously configures it. Alternatively, an attacker could set up an “evil twin” wireless hotspot that mimics the signal broadcast by a legitimate provider.
Bill Woodcock is executive director at Packet Clearing House, a nonprofit based in San Francisco. Woodcock said Option 121 has been included in the DHCP standard since 2002, which means the attack described by Leviathan has technically been possible for the last 22 years.
“They’re realizing now that this can be used to circumvent a VPN in a way that’s really problematic, and they’re right,” Woodcock said.
Woodcock said anyone who might be a target of spear phishing attacks should be very concerned about using VPNs on an untrusted network.
“Anyone who is in a position of authority or maybe even someone who is just a high net worth individual, those are all very reasonable targets of this attack,” he said. “If I were trying to do an attack against someone at a relatively high security company and I knew where they typically get their coffee or sandwich at twice a week, this is a very effective tool in that toolbox. I’d be a little surprised if it wasn’t already being exploited in that way, because again this isn’t rocket science. It’s just thinking a little outside the box.”
Successfully executing this attack on a network likely would not allow an attacker to see all of a target’s traffic or browsing activity. That’s because for the vast majority of the websites visited by the target, the content is encrypted (the site’s address begins with https://). However, an attacker would still be able to see the metadata — such as the source and destination addresses — of any traffic flowing by.
KrebsOnSecurity shared Leviathan’s research with John Kristoff, founder of dataplane.org and a PhD candidate in computer science at the University of Illinois Chicago. Kristoff said practically all user-edge network gear, including WiFi deployments, support some form of rogue DHCP server detection and mitigation, but that it’s unclear how widely deployed those protections are in real-world environments.
“However, and I think this is a key point to emphasize, an untrusted network is an untrusted network, which is why you’re usually employing the VPN in the first place,” Kristoff said. “If [the] local network is inherently hostile and has no qualms about operating a rogue DHCP server, then this is a sneaky technique that could be used to de-cloak some traffic – and if done carefully, I’m sure a user might never notice.”
According to Leviathan, there are several ways to minimize the threat from rogue DHCP servers on an unsecured network. One is using a device powered by the Android operating system, which apparently ignores DHCP option 121.
Relying on a temporary wireless hotspot controlled by a cellular device you own also effectively blocks this attack.
“They create a password-locked LAN with automatic network address translation,” the researchers wrote of cellular hot-spots. “Because this network is completely controlled by the cellular device and requires a password, an attacker should not have local network access.”
Leviathan’s Moratti said another mitigation is to run your VPN from inside of a virtual machine (VM) — like Parallels, VMware or VirtualBox. VPNs run inside of a VM are not vulnerable to this attack, Moratti said, provided they are not run in “bridged mode,” which causes the VM to replicate another node on the network.
In addition, a technology called “deep packet inspection” can be used to deny all in- and outbound traffic from the physical interface except for the DHCP and the VPN server. However, Leviathan says this approach opens up a potential “side channel” attack that could be used to determine the destination of traffic.
“This could be theoretically done by performing traffic analysis on the volume a target user sends when the attacker’s routes are installed compared to the baseline,” they wrote. “In addition, this selective denial-of-service is unique as it could be used to censor specific resources that an attacker doesn’t want a target user to connect to even while they are using the VPN.”
Moratti said Leviathan’s research shows that many VPN providers are currently making promises to their customers that their technology can’t keep.
“VPNs weren’t designed to keep you more secure on your local network, but to keep your traffic more secure on the Internet,” Moratti said. “When you start making assurances that your product protects people from seeing your traffic, there’s an assurance or promise that can’t be met.”
A copy of Leviathan’s research, along with code intended to allow others to duplicate their findings in a lab environment, is available here.
Amir Golestan, the 40-year-old CEO of the Charleston, S.C. based technology company Micfo LLC, has been sentenced to five years in prison for wire fraud. Golestan’s sentencing comes nearly two years after he pleaded guilty to using an elaborate network of phony companies to secure more than 735,000 Internet Protocol (IP) addresses from the American Registry for Internet Numbers (ARIN), the nonprofit which oversees IP addresses assigned to entities in the U.S., Canada, and parts of the Caribbean.
Amir Golestan, the former CEO of Micfo.
In 2018, ARIN sued Golestan and Micfo, alleging they had obtained hundreds of thousands of IP addresses under false pretenses. ARIN and Micfo settled that dispute in arbitration, with Micfo returning most of the addresses that it hadn’t already sold.
ARIN’s civil case caught the attention of federal prosecutors in South Carolina, who in May 2019 filed criminal wire fraud charges against Golestan, alleging he’d orchestrated a network of shell companies and fake identities to prevent ARIN from knowing the addresses were all going to the same buyer.
Prosecutors showed that each of those shell companies involved the production of notarized affidavits in the names of people who didn’t exist. As a result, the government was able to charge Golestan with 20 counts of wire fraud — one for each payment made by the phony companies that bought the IP addresses from ARIN.
Golestan initially sought to fight those charges. But on just the second day of his trial in November 2021, Golestan changed his mind and pleaded guilty to 20 counts of wire fraud in connection with the phantom companies he used to secure the IP addresses. Prosecutors estimated those addresses were valued at between $10 million and $14 million.
ARIN says the 5-year sentence handed down by the South Carolina judge “sends an important message of deterrence to other parties contemplating fraudulent schemes to obtain or transfer Internet resources.”
“Those who seek to defraud ARIN (or other Regional Internet Registries) are subject to costly and serious civil litigation, criminal charges, and, ultimately, a lengthy term of incarceration,” reads a statement from ARIN on Golestan’s sentencing.
By 2013, a number of Micfo’s customers had landed on the radar of Spamhaus, a group that many network operators rely upon to stem the tide of junk email. Shortly after Spamhaus started blocking Micfo’s IP address ranges, Micfo shifted gears and began reselling IP addresses mainly to companies marketing “virtual private networking” or VPN services that help customers hide their real IP addresses online.
Golestan did not respond to a request for comment. But in a 2020 interview with KrebsOnSecurity, Golestan claimed that Micfo was at one point responsible for brokering roughly 40 percent of the IP addresses used by the world’s largest VPN providers. Throughout that conversation, Golestan maintained his innocence, even as he explained that the creation of the phony companies was necessary to prevent entities like Spamhaus from interfering with his business going forward.
There are fewer than four billion so-called “Internet Protocol version 4” or IPv4 addresses available for use, but the vast majority of them have already been allocated. The global dearth of available IP addresses has turned them into a commodity wherein each IPv4 address can fetch between $15-$25 on the open market.
This has led to boom times for those engaged in the acquisition and sale of IP address blocks, but it has likewise emboldened those who specialize in absconding with and spamming from dormant IP address blocks without permission from the rightful owners.
The U.S Department of Justice says Golestan will serve 60 months in prison, followed by a 2-year term of court-ordered supervision. The Micfo CEO also was ordered to pay nearly $77,000 in restitution to ARIN for its work in assisting federal prosecutors.
The latest Jan. 6 committee hearing on Tuesday examined the role of conspiracy theory communities like 8kun[.]top and TheDonald[.]win in helping to organize and galvanize supporters who responded to former President Trump’s invitation to “be wild” in Washington, D.C. on that chaotic day. At the same time the committee was hearing video testimony from 8kun founder Jim Watkins, 8kun and a slew of similar websites were suddenly yanked offline. Watkins suggested the outage was somehow related to the work of the committee, but the truth is KrebsOnSecurity was responsible and the timing was pure coincidence.
In a follow-up video address to his followers, Watkins said the outage happened shortly after the Jan. 6 committee aired his brief video testimony.
“Then everything that I have anything to do with seemed to crash, so that there was no way for me to go out and talk to anybody,” Watkins said. “The whole network seemed to go offline at the same time, and that affected a lot of people.”
8kun and many other sites that continue to push the false narrative that the 2020 election was stolen from the 45th president have long been connected to the Internet via VanwaTech, a hosting firm based in Vancouver, Wash. In late October 2020, a phone call to VanwaTech’s sole provider of connectivity to the Internet resulted in a similar outage for 8kun.
Jim Waktins (top right), in a video address to his followers on Tuesday after 8kun was taken offline.
Following that 2020 outage, 8kun and a large number of QAnon conspiracy sites found refuge in a Russian hosting provider. But when the anonymous “Q” leader of QAnon suddenly began posting on 8kun again earlier this month, KrebsOnSecurity received a tip that 8kun was once again connected to the larger Internet via a single upstream provider based in the United States.
On Sunday, July 10, KrebsOnSecurity contacted Psychz Networks, a hosting provider in Los Angeles, to see if they were aware that they were the sole Internet lifeline for 8kun et. al. Psychz confirmed that in response to a report from KrebsOnSecurity, VanwaTech was removed from its network around the time of the Jan. 6 hearing on Tuesday.
8kun and its archipelago of conspiracy theory communities have once again drifted back into the arms of a Russian hosting provider (AS207651), which is connected to the larger Internet via two providers. Those include AS31500 — which appears to be owned by Russians but is making a fair pretense at being located in the Caribbean; and AS28917, in Vilnius, Lithuania.
8kun’s newfound Russian connections will likely hold, but Lithuania may be a different story. Late last month, pro-Russian hackers claimed responsibility for an extensive distributed denial-of-service (DDoS) attack against Lithuanian state and private websites, which reportedly was in response to Vilnius’s decision to cease the transit of some goods under European Union sanctions to Russia’s Kaliningrad exclave.
Many have speculated that Jim Watkins and/or his son Ron are in fact “Q,” the anonymous persona behind the QAnon conspiracy theory, which held that Former President Trump was secretly working to save the world from a satanic cult of pedophiles and cannibals.
8chan/8kun has been linked to white supremacism, neo-Nazism, antisemitism, multiple mass shootings, and is known for hosting child pornography. After three mass shootings in 2019 revealed the perpetrators had spread their manifestos on 8chan and even streamed their killings live there, 8chan was ostracized by one Internet provider after another.
In 2019, the FBI identified QAnon as a potential domestic terror threat, noting that some of its followers have been linked to violent incidents motivated by fringe beliefs.
The Jan. 6 hearing referenced in this story is available via CSPAN.
FreshRSS 