RegexExamples.md

KQL Regex List

This page will be used as a quick reference guide for KQL regex queries. Those regular expressions can be used within your detection rules. For additional information see the Regex RE2 Library from Microsoft.

To be able to easaly test your regeluar expressions the query below can be used:

let RegexTest = @'\W*((?i)Admin(?-i))\W*';
let DataSet = materialize (range numbers from 1 to 10 step 1);
DataSet
| extend StringTest = iff(numbers % 2  == 0, 'Admin', 'User') // Change Admin to a string that should match the RegexTest, change User to a string that should not match the RegexTest
| where StringTest matches regex RegexTest

IP

let IPRegex = '[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}';

Example query: AbuseCH IP Blacklist

Subnet

let IPv4SubnetRegex = '[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}/[0-9]{1,3}';

Example query:

let MISPFeed = externaldata(Subnet: string)[@"https://raw.githubusercontent.com/ktsaou/blocklist-ipsets/master/firehol_level1.netset"] with (format="txt", ignoreFirstRecord=True);
let IPv4SubnetRegex = '[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}/[0-9]{1,3}';
let x = MISPFeed 
| where Subnet matches regex IPv4SubnetRegex
| distinct Subnet;
x

Domain

let DomainRegex = @"([a-z0-9|-]+\.)*[a-z0-9|-]+\.[a-z]+";

Example query: Most Unusal Connections Made By office

File Extension

let FileExtensionRegex = "\\.([a-z])*";

Example query: Most Unusal Connections Made By office

Regex search for string

let DomainAdminRegex = @'\W*((?i)Domain Admins(?-i))\W*';

Example query:

let DomainAdminRegex = @'\W*((?i)Domain Admins(?-i))\W*'; // Replace Domain Admins with the string you would like to match on
DeviceProcessEvents
| where ProcessCommandLine matches regex DomainAdminRegex

Regex Parse Functionality

let BetweenTwoStrings = @'"Path":"([^"]*)"'; //Extract from "Path:""C:\Users\XX\File.txt" to collect C:\Users\XX\File.txt

Example query: Visualisation of the users with the most HardDelete actions performed (Line 8)

Regex Between Two Strings

let BetweenTwoStrings = @'findstr(.*)password';

Example query:

let BetweenTwoStrings = @'findstr(.*)password'; // Replace findstr and password with the strings you would like to match on
DeviceProcessEvents
| where ProcessCommandLine matches regex BetweenTwoStrings

Regex Between Last Char and String

let BetweenTwoStrings = @'.*/(.*)HTTP'; Between the last '/' and 'HTTP'. 

Example query: Executable File Extentions downloaded via HTTP GET (Line 11)

Regex Capture Everything After Char/String

let AfterChar = @'.*\.(.*)$'; // Capture all after last '.'. To collect file extentions.
let AfterString = @'.*test(.*)$';

Example query: Executable File Extentions downloaded via HTTP GET (Line 12)

Regex Between word and special char

let Regex = @'Role.DisplayName(.*?)"}'; Between Role.DisplayName until "}. 

Example query: List Role Additions (Line 5)

Regex Between two forward slashes

let Regex = @'\\(.*?)\\'; Between \ extra \ to escape and until \ and again an extra \ to excape. 

Example query: List Role Additions (Line 6)

File Hash

MD5

let MD5Regex = '[a-f0-9]{32}';

Example query: AbuseCH MD5 Malware Hash