They’re obviously doing recommendations based on IP address. (And this is purely over ipv4).
I have IPv6 at home and connect to Youtube over IPv6 (that's generally the default behaviour on macOS and many other OSes). I reboot my DSL modem-router every night and get a new IPv4 address and new IPv6 prefix every day.
Now: I live in Ontario, and my ISP is based in Ontario, but they serve clients in Quebec. Every so often, when surfing Youtube, I get served ads in French because according to my (IPv6) address I am "in" Quebec.
And, while I am not logged into any Google service, I do not block cookies. So even with cookies, Youtube seems to be fairly dumb about serving ads correctly just based on IP addresses (or at least IPv6 addresses and/or IPv6 prefixes), since cookies don't seem to be useful.
So I'm not quite sure about what people are talking about when they say "IPv6 tracking" if even Google/Youtube can't get their act together.
Iechyd Da!
eBay uses IPs showing content, too. I see 'items you've viewed recently' show items I've never looked at, since when on a mobile connection my IP changes fairly frequently and eBay carries over the recently viewed state from whoever else was previously using that IP.
It had puzzled me until I came across this[1] eBay topic where others had experienced this, from shared offices to spouses, etc.
[1] https://community.ebay.com/t5/Share-eBay-Technical-Issues/Re...
It's been available for some time: https://www.internetsociety.org/resources/deploy360/2014/pri...
On my macOS system, I currently have four IPv6 IPs (excluding the link-local IP), all of which are random.
For decades we have generally allowed all outbound and worried and fretted about and filtered inbound. I think it is time for us all to get a grip and do the job properly. However, with the delights of DNS over http and the like, the horse has not only bolted but has a new paint job, far better shoes than you can afford, eats grass that was prepared by a Michelin starred chef and belongs to someone else now.
We all need to be far more sophisticated about how traffic (knowledge/ideas/data) flows in and out of our networks/lives. Packet filtering is just one tool in the box and worrying about an addressing scheme being global (IPv6) instead of a weird hybrid (IPv4) is completely missing the real issue stabbing you in the nadgers.
the only thing you'd "leak" is the prefix, which is no different than a IPv4 WAN address that you'd get with a v4 NAT.
Assuming you block unsolicited packets (that is, packets not related to existing connections/streams) at your border (the connection to your ISP), then outsiders won't be able to use tools like traceroute to learn anything. All that an outsider has is an IPv6 IP, and since you're not doing BGP with anything, all they'll know to do is to send the traffic to your ISP.
I'm curious to know: what (attack) do you hope to protect against?
I would think that most attacks come in two fashions: the first being that you run a service of some kind and that there's some JSP/PHP/whatever exploit for a public facing service, and someone does a 'magic' PUT/GET that has the application server execute some code, which downloads a larger malware attack package. After which point the black hats start scanning from the inside.
The second being that someone clicks on a link in a phishing e-mail or executes some attachment, after which malware code starts scanning from the inside and phones home.
(A third being an insider attack, who presumably know about internal topology.)
What attack are you thinking to protect against by hiding subnet and VLAN topology?
And what are those vector(s)?
Besides compromising a machine that is already inside per the above (which can then do scanning / lateral moves), or perhaps physically getting inside the premises (in which case a scanner can be physically installed to examine the network), what attack are you protecting against?
Can you give me a link about an attack that knowing the topology of the network ahead of time would allow, but that not knowing would prevent?
Seems intellectually dishonest not to acknowledge that making things easier, just y'know, makes things easier. Keeping attackers, who want to do you harm, in the dark as much as possible seems important to me.
An attacker looking to be stealthy is not going to blast the network with nmap...
ARP is broadcast, NDP is solicited node multicast so simply by passively listening on the network you will discover nodes in the same layer 2 segment, with v6 and properly configured switches your passive discovery will be a lot more limited.
Other passive techniques would be monitoring things like DNS, and things the host you've compromised is actively communicating with. This isn't any different regardless of the protocol used.
You can also actively communicate with services like DNS or Active Directory and query information about the network, depending on your level of risk.
Just knowing the in-use IPv6 block is useless, the blocks are massive so even just identifying active hosts in a single known IPv6 block is a lot harder than simply scanning the entire RFC1918 legacy address space.
For active discovery, IPv6 is harder to attack - you can't scan the entire address block looking for hosts. The fact that such scans should be detected is exactly the same for either protocol. You also have to consider response time and what an attacker may be able to achieve before your response kicks in.
IPv6 makes it harder for attackers, not easier.