c-Internal Recon

Passive Recon

Start with reading internal network traffic.

Wireshark, tcpdump, net-creds, NetMiner

Look for active hosts, etc

ARP packets might provide list of hosts.

MDNS might provide hosts name.

Active Recon

fping

Quick ICMP sweep of the subnet using fping.

fping is similar to ping but can ping on list, and faster.

a to show targets that are alive, s to print stats at the end of the scan, g to generate a target list from the CIDR network, and q to not show per-target results.

jadu101@htb[/htb]$ fping -asgq 172.16.5.0/23
 
172.16.5.5
172.16.5.25
172.16.5.50
172.16.5.100
172.16.5.125
172.16.5.200
172.16.5.225
172.16.5.238
172.16.5.240

Nmap

Need to find out what services each host is running and identify critical hosts such as DC and web servers.

sudo nmap -v -A -iL hosts.txt

Identify Users

Most of the case, client won’t provide list of users.

We need credentials to establish foothold in the domain.

Clear-text password or an NTLM password hash for a user would be helpful.

Kerbrute

Kerbrute can be a stealthy option for domain account enumeraiton.

Kerberos pre-authenticaiton failure often doesn’t trigger alerts.

jsmith.txt or jsmith2.txt user lists from Insidetrust could be used.

Installation

sudo git clone https://github.com/ropnop/kerbrute.git

make help

sudo make linux

User Enum

jadu101@htb[/htb]$ kerbrute userenum -d INLANEFREIGHT.LOCAL --dc 172.16.5.5 jsmith.txt -o valid_ad_users
 
2021/11/17 23:01:46 >  Using KDC(s):
2021/11/17 23:01:46 >   172.16.5.5:88
2021/11/17 23:01:46 >  [+] VALID USERNAME:       jjones@INLANEFREIGHT.LOCAL
2021/11/17 23:01:46 >  [+] VALID USERNAME:       sbrown@INLANEFREIGHT.LOCAL
2021/11/17 23:01:46 >  [+] VALID USERNAME:       tjohnson@INLANEFREIGHT.LOCAL
2021/11/17 23:01:50 >  [+] VALID USERNAME:       evalentin@INLANEFREIGHT.LOCAL

Attack Paths

A SYSTEM account on a domain-joined host is able to enumerate AD by impersonating the computer account.

Having SYSTEM-level access within a domain environment is almost same as having a domain user account.

How to gain SYSTEM-level access on the host?

• MS08-067, EternalBlue, BlueKeep
• Abuse service running as SYSTEM account
• Abuse service account SeImpersonate privilege with Juicy Potato (Before Windows Server 2019)
• Local Privilege Escalation
• Lauching psexec with admin access on domain-joined host

What can we do with the SYSTEM-level access on a domain-joined host?

• Enumerate domain using tools such as Bloodhound and PowerView
• Kerberoasting
• ASREPRoasting
• Run Inveight to gather Net-NTLMv2 hashes
• SMB Relay Attack
• Token Impersonation to hijack privileged domain user account
• ACL Attacks