DNS-Changer – how to test your computer

There appears to have been an increase in attacks on private computers in recent weeks, and in some cases even a good virus scanner has not been able to block them.  Yesterday we learnt about a new threat called “DNS-Changer”.  This is what you need to know:

DNS is short for “Domain Name System” and is like a telephone directory for the internet.  When you visit a website, the address of that site is turned into the numeric address – the IP address – by a DNS server.  Your computer then uses the number to contact the site.  Cymeradwyo, for example, runs on IP address

The DNS servers for computers in private households are usually run by the internet providers such as T-Online.

But what would happen if instead of asking your internet provider for the IP address, your computer asked a different DNS server?  If this server gave and incorrect answer, the computer would pull up the wrong page.  Now if that page look different to the one you were expecting, then you would notice.  But what if it looks identical?

If that happened when you wanted to visit your bank’s website, then that could have serious consequences.  Even using a bookmark to visit the site or entering the address by hand does not help here.  The only way to tell may be to look at the small security padlock that most web browsers have – and even that might not always be the solution.

Such a system was recently active on the internet and was finally disabled in November of last year.  The German office for IT security (BSI) recommends that everyone in Germany now tests their computer, to see if it is one of the infected ones and is using an incorrect DNS server.

To test your system, simple click on this link: www.dns-ok.de.

A short message in German from the BSI, BKA and Deutschen Telekom tells you whether your computer has been infected.

For computers in companies that control their internet access or use a proxy server the situation is slightly different, so the test may not work.

But for everyone using their computer at home, and in most small businesses, if you do not see the “correct” website then your computer needs to be cleaned up.

If you want to do this yourself then there is a set of instructions (in German) on how to do this.  If you would like us to help you, then please send us a message using our contact form.


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About Graham

Graham Tappenden is a British ex-pat who first came to Germany as a placement student in 1993, returning in 1995 to live there permanently. He has been writing for AllThingsGerman.net since 2006. When not writing blog posts or freelancing for the Oberurseler Woche and other publications he works as a self-employed IT consultant solving computer problems and designing websites. In 2016 he gained German citizenship.


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