A security researcher made a tool that let them quickly check which of Cloudflare's data centers had cached an image, which allowed them to figure out what city a Discord, Signal, or Twitter/X user might be in.

cross-posted from: https://lemmy.ca/post/37638868 [email protected]

This affects Signal too

An issue with Cloudflare allows an attacker to find which Cloudflare data center a messaging app used to cache an image, meaning an attacker can obtain the approximate location of Signal, Discord, Twitter/X, and likely other chat app users. In some cases an attacker only needs to send an image across the app, with the target not clicking it, to obtain their location.

https://gist.github.com/hackermondev/45a3cdfa52246f1d1201c1e8cdef6117?ref=404media.co

Signal, an open-source encrypted messaging service, is widely used by journalists and activists for its privacy features. Internally, the app utilizes two CDNs for serving content: cdn.signal.org (powered by CloudFront) for profile avatars and cdn2.signal.org (powered by Cloudflare) for message attachments.

  • melroy@kbin.melroy.org
    31·
    12 hours ago

    So Unbound is actually a very powerful validating, recursive and caching DNS resolver. So without relaying on Google DNS or ISP DNS, you can host your own Unbound recursive DNS server, which can do request to other DNS servers and even root-dns servers. You can even setup your own stub zones and forward zones (sorry this is too much details I know). And like I said it also has caching feature. I will soon create a blog post about Unbound as well on my https://blog.melroy.org/ site be sure to subscribe.

    Here is a snipped of part of my config, feel free to use it however you want:

            # Serve stale data
        serve-expired: yes
        serve-expired-ttl: 86400           # one day, in seconds
        serve-expired-client-timeout: 500  # 500ms

        # Increase caches for better performance
        msg-cache-slabs: 4
        rrset-cache-slabs: 4
        infra-cache-slabs: 4
        key-cache-slabs: 4

        rrset-cache-size: 300m
        msg-cache-size: 150m

        outgoing-range: 200
        num-queries-per-thread: 100