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A regular expression (shortened as regex or regexp), [1] sometimes referred to as rational expression, [2] [3] is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings , or for input validation .
If the regex itself is affected by user input, such as a web service permitting clients to provide a search pattern, then an attacker can inject a malicious regex to consume the server's resources. Therefore, in most cases, regular expression denial of service can be avoided by removing the possibility for the user to execute arbitrary patterns ...
Email authentication, or validation, is a collection of techniques aimed at providing verifiable information about the origin of email messages by validating the domain ownership of any message transfer agents (MTA) who participated in transferring and possibly modifying a message.
The format of an email address is local-part@domain, where the local-part may be up to 64 octets long and the domain may have a maximum of 255 octets. [5] The formal definitions are in RFC 5322 (sections 3.2.3 and 3.4.1) and RFC 5321—with a more readable form given in the informational RFC 3696 (written by J. Klensin, the author of RFC 5321) and the associated errata.
The patterns generally have the form of either sequences or tree structures. Uses of pattern matching include outputting the locations (if any) of a pattern within a token sequence, to output some component of the matched pattern, and to substitute the matching pattern with some other token sequence (i.e., search and replace).
In computing, Bounce Address Tag Validation (BATV) is a method, defined in an Internet Draft, for determining whether the bounce address specified in an E-mail message is valid. It is designed to reject backscatter , that is, bounce messages to forged return addresses.
Raku rules are the regular expression, string matching and general-purpose parsing facility of the Raku programming language, and are a core part of the language. Since Perl's pattern-matching constructs have exceeded the capabilities of formal regular expressions for some time, Raku documentation refers to them exclusively as regexes, distancing the term from the formal definition.
Sender Policy Framework (SPF) is an email authentication method which ensures the sending mail server is authorized to originate mail from the email sender's domain. [1] [2] This authentication only applies to the email sender listed in the "envelope from" field during the initial SMTP connection.