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Attackers can decloak routing-based VPNs

leviathansecurity.com

21–30 of 238 posts

Re: Attackers can decloak routing-based VPNs

#21
post #3

Is there a tl;dr so we don't have to wade through swathes of AI generated text explaining what a network is?

I interviewed some smart people about their research in story published today:

https://krebsonsecurity.com/2024/05/why-your-vpn-may-not-be-...

Re: Attackers can decloak routing-based VPNs

#22
post #9

VPN can be trivially defeated any number of ways. I was shocked when I first learned this ten fifteen years ago through a site that showed my internet provider and location despite being on a VPN. I forgot the name of the site. A huge problem that doesn't even require defeating is, most OSs and VPN clients, if the connection is shaky, just reverts to the default connection. Even a single packet is enough for your VPN…

Are there any router/cheap "bridge" devices that can sit between your router and the internet and force outbound communication to go through the VPN, as if it were your ISP?

Just use iptables and only allow the vpn traffic. Or do the same with a small Linux box.

Re: Attackers can decloak routing-based VPNs

#23
post #10

The threat model is that an arbitrary attacker can somehow become the DHCP server on your LAN, which is unlikely but not impossible. On the other hand, if you are using an ISP provided gateway device..

Or become the DHCP server on whatever third party wifi you're connected to.

Re: Attackers can decloak routing-based VPNs

#24
post #14

always the breathless sensationalized vulnerability headlines... it's interesting, but of limited usefulness - the device has to accept responses from a dhcp server. if an attacker controls a dhcp server, he's either on the network already or has already had to do a lot worse than installing a couple static routes to get there. it's not nothing - a compromised home gateway could use this technique to sneak into a cor…

I think a public wifi network effectively being able to disable someone's VPN is pretty bad.

Re: Attackers can decloak routing-based VPNs

#25
There are numerous ways to defeat a VPN on a client device, this is why I prefer to put a router that terminates VPN tunnels with no other available routes between my clients and the Internet when I feel the need for a VPN. You can trivially set up one of these "travel routers" and carry it with you everywhere, which is exactly what I do.

Re: Attackers can decloak routing-based VPNs

#26
post #9

VPN can be trivially defeated any number of ways. I was shocked when I first learned this ten fifteen years ago through a site that showed my internet provider and location despite being on a VPN. I forgot the name of the site. A huge problem that doesn't even require defeating is, most OSs and VPN clients, if the connection is shaky, just reverts to the default connection. Even a single packet is enough for your VPN…

Are there any router/cheap "bridge" devices that can sit between your router and the internet and force outbound communication to go through the VPN, as if it were your ISP?

Pretty much any of the GL.iNet devices should be able to do that.

Re: Attackers can decloak routing-based VPNs

#28
post #9

VPN can be trivially defeated any number of ways. I was shocked when I first learned this ten fifteen years ago through a site that showed my internet provider and location despite being on a VPN. I forgot the name of the site. A huge problem that doesn't even require defeating is, most OSs and VPN clients, if the connection is shaky, just reverts to the default connection. Even a single packet is enough for your VPN…

Are there any router/cheap "bridge" devices that can sit between your router and the internet and force outbound communication to go through the VPN, as if it were your ISP?

On Linux this is easy with a network namespace and nftables.

Re: Attackers can decloak routing-based VPNs

#29
post #10

The threat model is that an arbitrary attacker can somehow become the DHCP server on your LAN, which is unlikely but not impossible. On the other hand, if you are using an ISP provided gateway device..

> arbitrary attacker can somehow become the DHCP server on your LAN, which is unlikely but not impossible

Coffee shop wi-fi? A.k.a merely the no. 1 selling point for most VPN offerings.

The proper course of action in this case is to use your 4G/5G connection and not to connect to shady networks you don't trust.

Re: Attackers can decloak routing-based VPNs

#30

Earlier quoted context omitted.

Are there any router/cheap "bridge" devices that can sit between your router and the internet and force outbound communication to go through the VPN, as if it were your ISP?

Just use iptables and only allow the vpn traffic. Or do the same with a small Linux box.

apparently lots of folks who do this still have problems that a lot of software that promises to do this actually only does it for ipv4, so ipv6 traffic still exposes them, lol
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