Homograph attack
A lookalike-domain attack that uses characters from other scripts which look identical to Latin letters, such as a Cyrillic a in place of a Latin a.
What it means
Unicode contains many characters that render the same as ASCII letters: Cyrillic а, е and о look like Latin a, e and o in most fonts. With internationalized domain names, an attacker can register a name that is visually identical to a known brand but is a different domain, stored in DNS as an xn-- A-label. Unicode's security report calls these visually confusable characters.
Unicode's security report gives recommendations for user agents, which it defines to include browsers and mail programs, such as showing the xn-- form of a suspicious name, and for registries, which can restrict the characters a domain may combine.
As with other lookalikes, the attacker controls the domain and can authenticate it, so SPF, DKIM and DMARC do not help.
Related terms
Sources
What this definition rests on. The wording is ours; the facts are theirs.
All 432 terms in the glossaryThe wiki: blocklists and bounce codes