With the help of LDAP Ping requests (cLDAP), “LDAP Nom Nom” is a powerful tool that quickly and quietly brute-forces Active Directory usernames. This piece goes into great detail about LDAP Nom Nom, explaining what it can do and how it might affect cybersecurity.

It works very quickly and can check usernames against multiple Domain Controllers at the same time with LDAP Nom Nom. It’s made to look for normal user accounts that are allowed without triggering Windows audit logs. This could make it a sneaky tool in the wrong hands.

We will look at its features, such as how it automatically finds Domain Controllers, how it uses multiple connections, and how it hides itself to avoid being found. The paper also talks about ways to find problems, ways to fix them, and the history of LDAP Ping requests.

Quietly and anonymously bruteforce Active Directory usernames at insane speeds from Domain Controllers by (ab)using LDAP Ping requests (cLDAP)

Looks for enabled normal user accounts. No Windows audit logs generated. High speed ~ up to 10K/sec – go beyond 25K/sec with multiple servers!

  • Tries to autodetect DC from environment variables on domain joined machines or falls back to machine hostname FQDN DNS suffix
  • Reads usernames to test from stdin (default) or file
  • Outputs to stdout (default) or file
  • Parallelized, multiple connections to multiple servers (defaults to 8 servers, 8 connections per server)
  • Shows progressbar if you’re using both input and output files
  • Evasive maneuvers: Use –throttle 20 for a 20ms delay between each request (slows everything down to a crawl)
  • Evasive maneuvers: Use –maxrequests 1000 to close connection and reconnect after 1000 requests in each connection (try to avoid detection based on traffic volume)

Download auto built binaries from releases or build and install with this Go command

go install github.com/lkarlslund/ldapnomnom@latest

Usage

ldapnomnom [--server dc1.domain.suffix[,dc2.domain.suffix] | --dnsdomain domain.suffix] [--port number] [--tlsmode notls|tls|starttls] [--input filename] [--output filename] [--parallel number-of-connections] [--maxservers number-of-servers] [--maxstrategy fastest|random] [--throttle n] [--maxrequests n]

Bruteforcing examples

Connect to up to 32 servers from contoso.local with 16 connections to each – FAAAAAAAST

ldapnomnom --input 10m_usernames.txt --output multiservers.txt --dnsdomain contoso.local --maxservers 32 --parallel 16

Connect to one named server with 4 connections

ldapnomnom --input 10m_usernames.txt --output results.txt --server 192.168.0.11 --parallel 4

Look for username lists to feed into this elsewhere – for instance the 10M list from here

Extract rootDSE attributes

You can also use LDAP Nom Nom to dump attributes from the rootDSE object, by adding the “–dump” option.

Connect to all servers you can find, and output all readable attributes to JSON:

ldapnomnom --output rootDSEs.json --dump

Detection

  • No Windows event logs are generated (tested on Windows 2016 / 2019)
  • Requires custom network level monitoring (unencrypted LDAP analysis or traffic volume for LDAPS)

Mitigation

  • None, this is part of the dcLocator stuff
  • Rename your administrator account
  • Audit accounts for having same password as the username
  • Prevent kerberoasting by removing SPNs on as many accounts as possible
  • Use long and complex passwords on accounts with SPNs