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by blueskin_ 4509 days ago
Firefox has its own DNS cache - emptying the normal cache in firefox also (silently) clears it.
1 comments
pfg 4509 days ago
Are you sure about that?

Here is what I've tried:

  ipconfig /displaydns | grep foobar.com
  #empty
  #open foobar.com in Firefox
  ipconfig /displaydns | grep foobar.com
    foobar.com
    Record Name . . . . . : foobar.com
  #delete firefox cache
  ipconfig /displaydns | grep foobar.com
    foobar.com
    Record Name . . . . . : foobar.com
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Dylan16807 4508 days ago
I think you misunderstood. Emptying the firefox data cache silently clears the firefox dns cache.
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pfg 4508 days ago
At which point the entry would still be cached by the OS, and since firefox apparently uses the OS API to resolve hostnames (if it didn't, I wouldn't have found the entry in my cache after opening the site, right?), it would still return the cached result (as long as it's not expired).

Besides, the question was how to prevent VAC from uploading your (hashed) DNS cache, and clearing Firefox cache doesn't flush those entries from your OS DNS cache.

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Dylan16807 4508 days ago
First off, in that case I'm not sure what your experiment was supposed to demonstrate.

More importantly, Windows will cache DNS records for no longer than the TTL. Firefox will keep entries in its cache for hours if not days. That's how sites you have been visiting will not show up in the OS cache.

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pfg 4508 days ago
OP asks if it's possible to block VAC from leaking your DNS cache (specifically the OS DNS cache obtainable via ipconfig /displaydns).

blueskin_ mentions that Firefox uses its own DNS cache, and deleting the browser cache also deletes the DNS entries.

However Firefox still uses the Windows API for DNS resolution, and deleting the browser cache doesn't result in those entries being flushed from the OS DNS cache (which is demonstrated by my experiment.) In other words, simply deleting your browser cache in Firefox will not prevent VAC from uploading your OS DNS cache. As long as the entries aren't expired or flushed manually, they will remain in your OS cache and VAC has no problem getting them.

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Dylan16807 4508 days ago
kamakazizuru asks if it's possible to block the leak

mdisraeli answers how, and remarks that many of the sites they're visiting are not in the cache

blueskin_ explains why those sites are not in the cache

pfg challenges blueskin_

Yes, 'some' of the sites will be cached by windows, this was explicitly stated in the original comment by mdisraeli. I don't know why you're acting like anyone is wrong. Did you skip midisraeli's comment accidentally, which lead you to think blueskin_ was offering a flawed solution to kamakazizuru? Blueskin_ was not offering any kind of VAC-related advice or information, just explaining Firefox's weirdness.

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