Configure Regular Expressions
Use the SaaS Security API regex builder to create expressions
that make content matching easy.
The regular expression builder in SaaS Security
API provides an easy mechanism to configure regular expressions
(regex for short), which you define when you create a custom data
pattern.
You can use the regular expression builder to construct a data pattern
expression, view matches, filter occurrences and weight thresholds,
and assess match results to determine if the content poses a risk
to your organization.
There are two types of regular expressions:
- basic expression—searches for a specific text pattern. When a pattern match is found, the service displays the match occurrences.
- weighted expression—assigns a score to a text entry. When the score threshold is exceeded, such as enough expressions from a pattern match an asset, the service returns a match for the pattern.To reduce false-positives and maximize the search performance of your regular expressions, you can assign scores using the weighted regular expression builder in SaaS Security API to find and calculate scores for the information that is important to you. Scoring applies a match threshold, and when a threshold is exceeded, such as enough words from a pattern are found in a document, the document will be indicated as a match for the pattern.
Use
Case: Calculating and Scoring a weighted regular expression
For
example, Joe is an employee at a water treatment plant and needs
to compile user data on a proprietary pH additive that is used when
source water arrives at the plant. If Joe initiated a regular expression
search with just the term "tap water" thousands of match results
display, as the matched tap water documents list the additive, but
Joe is really searching for the first use of the additive, not every
document the additive is listed in, making it difficult for Joe
to find the usage data he needs.
To get more accurate results,
Joe can initiate a weighted regular expression to assign weight
and occurrence scores to the expression, or indicate the information
to exclude by assigning a negative weight value.
Joe enters
a negative weight value to exclude tap water and higher values to
source water and the proprietary water additive. The results are
filtered and counted to a more manageable list, meaning that a document
containing 10 occurrences of water counts as one when all files
and folders are scanned. This enables Joe to view the match results,
adjust the totals for weight and occurrences, and calculate an adjusted
score to determine if the content poses a risk to his organization.
Weighted Regex Item | Occurrence | Adjusted Occurrence Score | Adjusted Total |
---|---|---|---|
Water; 1 | 50 | 50 (1 Occurrence X 1) | 110 minus 100 for tap water
= 10 regex weight |
IP pH; 2 | 30 | 60 (30 occurrences X 2) | |
Tap Water; -10 | 10 | -100 (10 occurrences x -10) |
- Consider the best practices for using regular expression matches.
- Use predefined data patterns instead of regular expressions. Use SaaS Security API predefined data patterns instead of regular expressions where possible. Data patterns are more efficient than regular expressions because the predefined data patterns are tuned for accuracy and the data is validated. For example, if you want to search for social security numbers, use the US Social Security Number (SSN) data pattern instead of a regular expression.
- Use regular expressions sparingly. Regular expressions can be computationally expensive. If you add a regular expression condition, observe the system for one hour for efficient performance. Make sure that the system does not slow down and there are no false positives.
- Test regular expressions. If you implement regular expression matching, consider using a third-party tool to test the regular expressions before you enable the policy rules. The recommended tool is RegexBuddy. Another good tool for testing your regular expressions is RegExr. If your expression is incorrect, the service cannot match or will match incorrectly.
- Understand expression terminology.Expression Terminology:TermDescriptionLiteralA literal is any character you use in a search or matching expression, for example, to find dlp in SaaS Security API, "dlp" is a literal string - each character plays a part in the search, it is literally the string we want to find.MetacharacterA metacharacter is one or more special characters that have a unique meaning and are NOT used as literals in the search expression, for example, the character < > (caret) is a metacharacter.Regular ExpressionThis term describes the search expression data pattern that you will be using to search in SaaS Security API.Escape SequenceAn escape sequence is a way of indicating that you want to use one of the metacharacters as a literal. In a regular expression an escape sequence involves placing the metacharacter \ (backslash) in front of the metacharacter that you use as a literal, for example, if you want to find (dlp) in SaaS Security API then use the search expression \(dlp\), and if you want to find \\file in the target string c:\\file then you would need to use the search expression \\\\file (each \ to search for a literal (there are 2) that is preceded by an escape sequence \).
- Understand expression constructs.SaaS Security API implements the Java regular syntax for policy condition matching. SaaS Security API provides some common reference constructs for writing regular expressions to match or exclude characters in content.Regular expression constructs:ConstructDescription.A dot, any single character, except newline (line ending, end of line, or line break) characters.\Escape the next character (the character becomes a normal/literal character.)\dAny digit (0-9.)\sAny white space.\WAny word character (a-z, A-Z, 0-9.)\DAnything other than a digit.\SAnything other than a white space.[ ]Elements inside brackets are a character class (for example, [abc] matches 1 character [a. b. or c.]^At the beginning of a character class, negates it (for example, [^abc] matches anything except (a, b, or c.)$At the end of a character class, or before newline at the end.+Following a regular expression means 1 or more (for example, \d+ means 1 more digit.)?Following a regular expression means 0 or 1 (for example, \d? means 1 or no digit.)*Following a regular expression means any number (for example \d* means 0, 1, or more digits.)(?i)At the beginning of a regular expression makes it case-insensitive (regular expressions are case-sensitive by default.)( )Groups regular expressions together.(?u)Makes a period ( . ) match to even newline characters.|Means OR (for example, A|B means regular expression A or regular expression B.)
- Understand expression qualifiers.Quantifiers can be used to specify the number or length that part of a pattern should match or repeat. A quantifier will bind to the expression group to its immediate left.Regular expression quantifiers:QuantifierDescription*Match 0 or more times.+Match 1 or more times.?Match 1 or 0 times.{n}Match exactly n times.{n, }Match at least n times.{n, m}Match at least n but not more than m times.
- Enter one regular expression per line, up to 100 lines of expressions.
- (Weighted expressions only): Assign a regular expression for each line entry between-9999(lowest importance) to9999(highest importance) by entering the regular expression, the delimiter, and the weight score. You must enter a weight threshold score of one (1) of more.
- (Optional) Customize your delimiter.By default, the delimiter for all weighted regular expressions is semicolon ( ; ). You can customize your delimiter to copy and paste existing expressions instead of entering them manually. A delimiter is used to specify separate strings of data when configuring regular expressions. For example, you can configure a weighted regular expression using a delimiter to separate the string of text you are matching from the weight threshold value. If you have large amounts of existing expressions to match, you can customize your delimiter to copy and paste the expressions instead of entering them manually. A delimiter can be any non-alphanumeric, non-backslash, non-whitespace character.Regular expression delimiters:DelimiterNote;Semicolon — If the delimiter is not customized, the semicolon is the default delimiter in SaaS Security API.:Colon.|Pipe./Forward Slash — If the delimiter needs to be matched inside the pattern it must be escaped using a backslash ( \ ). If the delimiter appears often inside the pattern, it is a good idea to choose another delimiter to increase readability.+Plus — Include phrase for matching.-Minus — Ignore phrase for matching.#Hash — Can be used to denote a number.~Tilde{ } CurlyBrackets are used to find a range of characters. Bracket style delimiters do not need to be escaped when they are used as meta characters within the pattern, but they must be escaped when they are used as literal characters.[ ] Square( ) Parenthesis< > Caret
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