If you have a shared computer and you think that by deleting the history you can eliminate all traces of the pages you have visited, you are making a mistake. Even if we use incognito mode offered by most web browsers, the truth is that there is always a loophole where all those "private" visits are recorded, and that is DNS cache.
What is DNS cache exactly?
When we write the name of a web page in the address bar of the browser, it goes to the DNS server that we have configured in our device to know what IP it corresponds to and load the content of the page. Thus, when we later try to access that same site, our browser consults the DNS cache, and if it is in the list, it resolves the address without having to consult the IP address on the server.
This is a pretty smart trick that allows us to navigate and load the pages much faster, as well as send emails and perform other types of actions through the Internet. The funny thing about all this is that the DNS cache does not distinguish between the different types of navigation, and records everything: both normal tabs and those that work in "incognito mode".
How to see the websites that we have visited in incognito mode from the DNS cache
Since DNS is totally independent of the browser we are using, this is a trick that we can apply both for the websites visited in Chrome, like Firefox, Edge, Opera or any other browser.
To consult the list of pages registered in the DNS cache, all we have to do is execute a command from an MS-DOS or Powershell window on the computer.
- We open an MS-DOS window in Windows by typing the command "cmd”In Cortana's browser. If we have an older version of Windows we can also enter this same command from "Start -> Run”.
- Terminal windows usually open to the path where the active user profile is located, such as "C: \ Users \ User_name”. The first thing we are going to do is place ourselves at the desk, typing the command "cd desktop”.
- Next, we write the command "ipconfig / displaydns> historialdns.txt”. This will cause the system to dump all DNS cached history into a text file called "historialdns.txt".
Now we only have to go to the desktop and open the text file that has just been created. We will see how a list appears with all the web pages and services we have visited recently, including those "private" websites that have been loaded in incognito mode.
Note: We can also see the contents of the DNS cache directly from the MS-DOS window by typing the command "ipconfig / displaydns”. However, the cache usually includes a large number of entries and in many cases it is impractical to consult, so I personally think that it is much more convenient to dump it in a TXT file.
How to flush the DNS cache
If we are concerned that someone might spy on us with this method, we can always clear the DNS cache. To do this, just open a new MS-DOS window and execute the command "ipconfig / flushdns”.
In general, it is recommended to clear the DNS cache from time to time for both security and privacy reasons. However, it can also help us solve technical problems, in the event that a page does not load correctly or shows any DNS errors.
If we are Android users, although we cannot see the content of the DNS resolution cache, we can simply empty it turning off the phone for at least a minute and turning the device back on.
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