Have a look at the following domainnames: www.my-bank.com and www.my-bаnk.com seem to be the same domain names at first glance, but they are definitely different. Last one contains a Cyrillic a, not a Latin a: www.my-bаnk.com.

Domainnames containing one or more characters outside the Latin character set (a-z) and (0-9) are "internationalized domainname" (shortform IDN).

• The introduction of the standard for "internationalized domainnames" has been an enormous progress towards a "real" opening of the World Wide Web to the whole world. With the ability to use Domain Names with Chinese or Cyrillic characters common in Asian, Arabic, Eastern European ... Countries "these will be able to create an identity adequate to their linguistic culture in the World Wide Web".

Security Aspect

• Registering domainnames staying outside the old character set gives the possibility to register domainnames with international letters that are identical to other international or Latin alphabetic letters. Spoofing names of existing important organisations criminals can register an infinite range of valid domain names. Since there is a valid domain name behind the scenes these deception-based phishing attacks are nearly impossible to identify by normal internet users.
  
  An internationalized domainname like www.my-bаnk.com containing for example a Cyrillic character can be used for phishing attacks.

 

As an answer to the problem of IDN homograph attacks the "IDN Char Collision Detection Protocol"  IdnCCDTm Protocol. has been developed.

• the Char Collision Detection part filters your web requests for domain names containing characters that are similar to other characters.
• the Trust management part notifies you before continuing with the request, informs you about the detected idn char collision in the current web request and gives you the possibility to decide whether to trust or reject the request.

The IdnCCDTm Protocol therefore

• guarantees an effective and secure way of browsing the web of internationalised domains because it is concentrated on homographic properties of international characters
• guarantees a smart and moderate way of browsing the web of internationalised domains that does not discriminate against the nature of an "Internationalised Domain Name". That means the "authentic character" of "Internationalised Domains" will be maintained".

IdnWebShield is the worldwide first software that implements Idn char collision detection.