4 ms·

Not just HTTP, there is plenty of information in lower layers too. For example, this page will show your exact computer uptime, down to the millisecond, using t

by kvbr 12y ago

Not just HTTP, there is plenty of information in lower layers too. For example, this page will show your exact computer uptime, down to the millisecond, using the tcp/ip timestamp feature (OS dependent, works on linux kernels 3.12+ and some Windows and Mac versions): http://lcamtuf.coredump.cx/p0f3/ http://lcamtuf.coredump.cx/p0f3/ 10-20 bits of entropy right there (you need 33 bits of entropy to uniquely identify 1 of 6.6 billion people on earth). ...or traceroute of the user's routers, done within the confines of an existing TCP/IP connection, bypassing every stateful firewall and address translation (exhibit 3 in page): http://lcamtuf.coredump.cx/mobp/ http://lcamtuf.coredump.cx/mobp/

deathanatos 12y ago
I get some odd results: HTTP client = Opera 15.x-18.x (User-Agent string is fake) I'm on Chrome, and not faking a User-Agent. Uptime = 9 days 17 hrs 17 min (modulo 49 days) This is just wrong. Everything else was correct, but everything else is available in HTTP headers, so isn't really that interesting. > 10-20 bits of entropy right there (you need 33 bits of entropy to uniquely identify 1 of 6.6 billion people on earth). This reminds me of this[1]. [1]: https://panopticlick.eff.org/ https://panopticlick.eff.org/
- kvbr 12y ago
  You may be behind a transparent proxy, or have a user-agent string not in P0f tool database. Vardump: notice that you get almost the same uptime for your Mac and your Windows PC: 19 days 18 hrs 10 min. It appears your router (NAT) is handling / modifying the tcp/ip timestamp. Btw, even if the timestamp is wrong, it can provide some entropy (=measure of uniqueness compared to other users).
- vardump 12y ago
  What I get is very similar (newest Chrome + Yosemite): Detected OS = Mac OS X [generic] HTTP client = Opera 15.x-18.x (User-Agent string is fake) Network link = unknown Distance = 11 Language = English Uptime = 19 days 18 hrs 10 min (modulo 71 days) (Uptime is off by 10 days, real uptime is 29 days.) Or Windows 10 + newest Chrome: Detected OS = Windows 7 or 8 HTTP client = Opera 15.x-18.x (User-Agent string is fake) Network link = Ethernet or modem Distance = 11 Language = English Uptime = 19 days 18 hrs 10 min (modulo 71 days) (Uptime is off by 14 days, real uptime is about 5 days.) No transparent proxies, just NAT, both systems share IP.
  - gaadd33 12y ago
    I wonder if your NAT device has an uptime of 19 days.
    - vardump 12y ago
      Nope, 31 days uptime on the NAT router.
TheLoneWolfling 12y ago
I see no indication of uptime on that page? > Detected OS = Windows 7 or 8 > HTTP client = Firefox 10.x or newer (User-Agent string seems legit) > Network link = DSL > Distance = 10 > Language = English

by kvbr 12y ago

deathanatos 12y ago

I get some odd results: HTTP client = Opera 15.x-18.x (User-Agent string is fake) I'm on Chrome, and not faking a User-Agent. Uptime = 9 days 17 hrs 17 min (modulo 49 days) This is just wrong. Everything else was correct, but everything else is available in HTTP headers, so isn't really that interesting. > 10-20 bits of entropy right there (you need 33 bits of entropy to uniquely identify 1 of 6.6 billion people on earth). This reminds me of this[1]. [1]: https://panopticlick.eff.org/ https://panopticlick.eff.org/

kvbr 12y ago
You may be behind a transparent proxy, or have a user-agent string not in P0f tool database. Vardump: notice that you get almost the same uptime for your Mac and your Windows PC: 19 days 18 hrs 10 min. It appears your router (NAT) is handling / modifying the tcp/ip timestamp. Btw, even if the timestamp is wrong, it can provide some entropy (=measure of uniqueness compared to other users).
vardump 12y ago
What I get is very similar (newest Chrome + Yosemite): Detected OS = Mac OS X [generic] HTTP client = Opera 15.x-18.x (User-Agent string is fake) Network link = unknown Distance = 11 Language = English Uptime = 19 days 18 hrs 10 min (modulo 71 days) (Uptime is off by 10 days, real uptime is 29 days.) Or Windows 10 + newest Chrome: Detected OS = Windows 7 or 8 HTTP client = Opera 15.x-18.x (User-Agent string is fake) Network link = Ethernet or modem Distance = 11 Language = English Uptime = 19 days 18 hrs 10 min (modulo 71 days) (Uptime is off by 14 days, real uptime is about 5 days.) No transparent proxies, just NAT, both systems share IP.
- gaadd33 12y ago
  I wonder if your NAT device has an uptime of 19 days.
  - vardump 12y ago
    Nope, 31 days uptime on the NAT router.

TheLoneWolfling 12y ago

I see no indication of uptime on that page? > Detected OS = Windows 7 or 8 > HTTP client = Firefox 10.x or newer (User-Agent string seems legit) > Network link = DSL > Distance = 10 > Language = English