Kerbrute – a tool to perform kerberos pre-auth bruteforcing

Kerbrute – a tool to perform kerberos pre-auth bruteforcing

Kerbrute – a tool to perform kerberos

A tool to quickly bruteforce and enumerate valid Active Directory accounts through Kerberos Pre-Authentication
Grab the latest binaries from the releases page to get started.

Background

This tool grew out of some bash scripts I wrote a few years ago to perform bruteforcing using the Heimdal Kerberos client from Linux. I wanted something that didn’t require privileges to install a Kerberos client, and when I found the amazing pure Go implementation of Kerberos gokrb5, I decided to finally learn Go and write this.
Bruteforcing Windows passwords with Kerberos is much faster than any other approach I know of, and potentially stealthier since pre-authentication failures do not trigger that “traditional” An account failed to log on event 4625. With Kerberos, you can validate a username or test a login by only sending one UDP frame to the KDC (Domain Controller)
For more background and information, check out my Troopers 2019 talk, Fun with LDAP and Kerberos (link TBD).

Usage

Kerbrute has three main commands:

bruteuser – Bruteforce a single user’s password from a wordlist
passwordspray – Test a single password against a list of users
usernenum – Enumerate valid domain usernames via Kerberos

A domain (-d) or a domain controller (–dc) must be specified. If a Domain Controller is not given the KDC will be looked up via DNS.
By default, Kerbrute is multithreaded and uses 10 threads. This can be changed with the -t option.
Output is logged to stdout, but a log file can be specified with -o.
By default, failures are not logged, but that can be changed with -v.
Lastly, Kerbrute has a –safe option. When this option is enabled, if an account comes back as locked out, it will abort all threads to stop locking out any other accounts.

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