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ICANN Computer Incident Response Team



ICANN CIRT is the corporate Computer Incident Response Team for the Internet Corporation for Assigned Names and Numbers.

ICANN CIRT is not a public IT helpdesk and will not respond to questions having to do with matters unrelated to ICANN internal corporate security such as spam or domain registration disputes.

If you wish to report a security issue involving your web domain, please contact your registrar directly. If you believe you are being attacked by IANA assigned IP addresses please visit this page: to, or send email to:


ICANN CIRT: ICANN Computer Incident Response Team
CIRT email: icanncirt [at] icann [dot] org
Mailing Address: ICANN
12025 Waterfront Drive, Suite 300 Playa Vista, CA 90094
Telephone Voice: +1 310 301 5800

Contacting ICANN Computer Incident Response Team

  • If you are investigating an incident where ICANN corporate resources are involved or at risk, please call: +1 310 301 5800 and ask for the Information Security team.
  • Confidential communications with the ICANN Computer Incident Response Team may be encrypted using the public key for ICANN CIRT:

CIRT Team PGP Key fingerprint = 0CE2 8CA5 EEA1 AC7E 3F64  14EA E6EC EC9A 217D E93A

Domain Name System
Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as"""" is not an IDN."