What’s a DNS Cache?

A DNS Cache is a part of an OS (Operating System) that tracks and keeps information about websites or internet domains that you have connected to or tried to connect to. Even if you clear your internet history or browsing data in your browser, the DNS Cache will still retain the IP Addresses of each website it has indexed.

DNS Cache Poisoning

Your DNS Cache can become “poisoned”  when a malicious IP Address or Domain name is inserted into it. When your DNS Cache has been poisoned you will be directed to malicious websites. DNS Cache poisoning can also help aid in phishing attacks. Lets say your DNS Cache has been poisoned and you try to connect to your banking website. If an attacker creates a fake clone of that website and makes it so your computer goes to their fake site they could potentially steal your login credentials. All because you thought it was your banks legitimate site.

How to flush your DNS

If you’re running Windows you’re going to want to open a command prompt window to start with. Then to see your DNS Cache type in “ipconfig/displaydns” without the quotes. You should see a list of all the different connections. To flush it type in “ipconfig/flushdns” without the quotes. If everything works alright then you should see a message that says something along the lines of “Successfully flushed the DNS Resolver Cache.” You can then exit command prompt and you’re all set!

If you’re running MacOS you have to open a command terminal and type “dscacheutil-flushcache” without the quotes. Unlike Windows you will not get a message stating if it was successful or not.

If you’re running Linux you need to open a terminal and type “/etc/rc.d/init.d/nscd restart” without the quotes. If that doesn’t work you will want to make sure you are logged in as a root user.




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