CompTIA PT0-003 - CompTIA PenTest+ Exam

The ms17_010_eternalblue exploit is the most appropriate choice based on the scenario.

Why MS17-010 EternalBlue?

EternalBlue is a critical vulnerability in SMBv1 (port 445) affecting older versions of Windows, including Windows 7.

The exploit can be used to execute arbitrary code remotely, providing shell access to the target system.

Other Options:

A (psexec): This exploit is a post-exploitation tool that requires valid credentials to execute commands remotely.

B (ms08_067_netapi): A vulnerability targeting older Windows systems (e.g., Windows XP). It is unlikely to work on Windows 7.

D (snmp_login): This is an auxiliary module for enumerating SNMP, not gaining shell access.

CompTIA Pentest+ References:

Domain 2.0 (Information Gathering and Vulnerability Identification)

Domain 3.0 (Attacks and Exploits)

Correct Syntax for a Range Loop in Bash:

The seq command generates a sequence of numbers in a specified range, which is ideal for iterating over IP addresses in a Class C subnet (1–254).

Example: seq 1 254 will output numbers 1, 2, ..., 254 sequentially.

Explanation of Other Options:

A (crunch): The crunch command is used for wordlist generation and is unrelated to looping in Bash.

C (echo 1-254): This would output "1-254" as a string instead of generating a numeric range.

D ({1.-254}): This is incorrect Bash syntax and would result in a script error.

Final Script:

bash

for var in $(seq 1 254)

do

ping -c 1 192.168.10.$var

done

CompTIA Pentest+ References:

Domain 4.0 (Penetration Testing Tools)

Bash Scripting and Automation

The command that would most likely exploit the services is:

hydra -l lowpriv -P 500-worst-passwords.txt -t 4 ssh://192.168.10.2:22

The appropriate set of commands to escalate privileges is:

echo "root2:5ZOYXRFHVZ7OY::0:0:root:/root:/bin/bash" >> /etc/passwd

The remediations that should be taken after the successful privilege escalation are:

Remove the SUID bit from cp.

Make backup script not world-writable.

Comprehensive Step-by-Step Explanation of the Simulation

Part 1: Exploiting Vulnerable Service

Nmap Scan Analysis

Command: nmap -sC -T4 192.168.10.2

Purpose: This command runs a default script scan with timing template 4 (aggressive).

Output:

bash

Copy code

Port State Service

22/tcp open ssh

23/tcp closed telnet

80/tcp open http

111/tcp closed rpcbind

445/tcp open samba

3389/tcp closed rdp

Ports open are SSH (22), HTTP (80), and Samba (445).

Enumerating Samba Shares

Command: enum4linux -S 192.168.10.2

Purpose: To enumerate Samba shares and users.

Output:

makefile

Copy code

user:[games] rid:[0x3f2]

user:[nobody] rid:[0x1f5]

user:[bind] rid:[0x4ba]

user:[proxy] rid:[0x42]

user:[syslog] rid:[0x4ba]

user:[www-data] rid:[0x42a]

user:[root] rid:[0x3e8]

user:[news] rid:[0x3fa]

user:[lowpriv] rid:[0x3fa]

We identify a user lowpriv.

Selecting Exploit Command

Hydra Command: hydra -l lowpriv -P 500-worst-passwords.txt -t 4 ssh://192.168.10.2:22

Purpose: To perform a brute force attack on SSH using the lowpriv user and a list of the 500 worst passwords.

-l lowpriv: Specifies the username.

-P 500-worst-passwords.txt: Specifies the password list.

-t 4: Uses 4 tasks/threads for the attack.

ssh://192.168.10.2:22: Specifies the SSH service and port.

Executing the Hydra Command

Result: Successful login as lowpriv user if a match is found.

Part 2: Privilege Escalation and Remediation

Finding SUID Binaries and Configuration Files

Command: find / -perm -2 -type f 2>/dev/null | xargs ls -l

Purpose: To find world-writable files.

Command: find / -perm -u=s -type f 2>/dev/null | xargs ls -l

Purpose: To find files with SUID permission.

Command: grep "/bin/bash" /etc/passwd | cut -d':' -f1-4,6,7

Purpose: To identify users with bash shell access.

Selecting Privilege Escalation Command

Command: echo "root2:5ZOYXRFHVZ7OY::0:0:root:/root:/bin/bash" >> /etc/passwd

Purpose: To create a new root user entry in the passwd file.

root2: Username.

5ZOYXRFHVZ7OY: Password hash.

0:0: User and group ID (root).

/root: Home directory.

/bin/bash: Default shell.

Executing the Privilege Escalation Command

Result: Creation of a new root user root2 with a specified password.

Remediation Steps Post-Exploitation

Remove SUID Bit from cp:

Command: chmod u-s /bin/cp

Purpose: Removing the SUID bit from cp to prevent misuse.

Make Backup Script Not World-Writable:

Command: chmod o-w /path/to/backup/script

Purpose: Ensuring backup script is not writable by all users to prevent unauthorized modifications.

Execution and Verification

Verifying Hydra Attack:

Run the Hydra command and monitor for successful login attempts.

Verifying Privilege Escalation:

After appending the new root user to the passwd file, attempt to switch user to root2 and check root privileges.

Implementing Remediation:

Apply the remediation commands to secure the system and verify the changes have been implemented.

By following these detailed steps, one can replicate the simulation and ensure a thorough understanding of both the exploitation and the necessary remediations.

Based on the CVSS (Common Vulnerability Scoring System) and EPSS (Exploit Prediction Scoring System) scores, Target 1 is the most likely to get attacked.

CVSS:

Definition: CVSS provides a numerical score to represent the severity of a vulnerability, helping to prioritize the response based on the potential impact.

Score Range: Scores range from 0 to 10, with higher scores indicating more severe vulnerabilities.

EPSS:

Definition: EPSS estimates the likelihood that a vulnerability will be exploited in the wild within the next 30 days.

Score Range: EPSS scores range from 0 to 1, with higher scores indicating a higher likelihood of exploitation.

Analysis:

Target 1: CVSS = 4, EPSS = 0.6

Target 2: CVSS = 2, EPSS = 0.3

Target 3: CVSS = 1, EPSS = 0.6

Target 4: CVSS = 4.5, EPSS = 0.4

Target 1 has a moderate CVSS score and a high EPSS score, indicating it has a significant vulnerability that is quite likely to be exploited.

Pentest References:

Vulnerability Prioritization: Using CVSS and EPSS scores to prioritize vulnerabilities based on severity and likelihood of exploitation.

Risk Assessment: Understanding the balance between impact (CVSS) and exploit likelihood (EPSS) to identify the most critical targets for remediation or attack.

By focusing on Target 1, which has a balanced combination of severity and exploitability, the penetration tester can address the most likely target for attacks based on the given scores.

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DIR_MODE=0777 configures new home directories to be created world-readable, world-writable, and world-executable (rwxrwxrwx). With such permissive permissions, any unprivileged local user can traverse into other users’ home directories, list files, read them, and even modify or replace them. That makes exposure of other users’ sensitive data the most likely and immediate outcome once the tester has any local user account.

Why the other options are less likely:

B. Unauthorized sudo execution: Requires membership in sudo/wheel or explicit entries in /etc/sudoers. Nothing in the snippet indicates that, and file mode on home dirs doesn’t grant sudo.

C. Hijacking default login shells: DSHELL=/bin/zsh only sets the default shell for new users. Replacing /bin/zsh or altering /etc/passwd would require root.

D. Corrupting the skeleton configuration: SKEL=/etc/systemd-conf/temp-skeleton is under /etc/…, which is root-owned on standard systems. A normal user cannot write there, so “corrupting the skeleton” is unlikely without privilege escalation.

Practical exploitation as a non-privileged user (illustrative):

# Find world-writable homes

find /home -maxdepth 1 -type d -perm -0002 -ls

# Read another user's files

cd /home/targetuser && ls -la && cat Documents/tax_return.pdf

(Depending on per-file permissions.)

CompTIA PenTest+ PT0-003 Objective Mapping (for study):

Domain 3.0 Attacks and Exploits

3.1 Exploit system vulnerabilities and misconfigurations (e.g., insecure file permissions leading to data exposure/privilege abuse).

Web shells provide remote access and persistence for attackers. The best mitigation is to remove persistence mechanisms.

Remove the persistence mechanisms (Option A):

Attackers often modify startup scripts, cron jobs, or registry keys to maintain access.

If persistence is not removed, even after the web shell is deleted, attackers can reinstall or reaccess it.

To maintain access to a compromised system after rebooting, a penetration tester should create a scheduled task. Scheduled tasks are designed to run automatically at specified times or when certain conditions are met, ensuring persistence across reboots.

Persistence Mechanisms:

Scheduled Task: Creating a scheduled task ensures that a specific program or script runs automatically according to a set schedule or in response to certain events, including system startup. This makes it a reliable method for maintaining access after a system reboot.

Reverse Shell: While establishing a reverse shell provides immediate access, it typically does not survive a system reboot unless coupled with another persistence mechanism.

Process Injection: Injecting a malicious process into another running process can provide stealthy access but may not persist through reboots.

Credential Dumping: Dumping credentials allows for re-access by using stolen credentials, but it does not ensure automatic access upon reboot.

Creating a Scheduled Task:

On Windows, the schtasks command can be used to create scheduled tasks. For example:

schtasks /create /tn "Persistence" /tr "C:\path\to\malicious.exe" /sc onlogon /ru SYSTEM

On Linux, a cron job can be created by editing the crontab:

(crontab -l; echo "@reboot /path/to/malicious.sh") | crontab -

Pentest References:

Maintaining persistence is a key objective in post-exploitation. Scheduled tasks (Windows Task Scheduler) and cron jobs (Linux) are commonly used techniques.

References to real-world scenarios include creating scheduled tasks to execute malware, keyloggers, or reverse shells automatically on system startup.

By creating a scheduled task, the penetration tester ensures that their access method (e.g., reverse shell, malware) is executed automatically whenever the system reboots, providing reliable persistence.

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Since SSID broadcast might be hidden, channel scanning allows the tester to identify active Wi-Fi networks.

Option A (Sidecar scanning) ❌: Not a recognized Wi-Fi testing method.

Option B (Channel scanning) ✅: Correct.

Identifies hidden SSIDs by monitoring probe requests and responses.

Option C (Stealth scanning) ❌: Typically refers to evading detection, not Wi-Fi analysis.

Option D (Static analysis scanning) ❌: Static analysis applies to code security, not Wi-Fi networks.

📖 Reference: CompTIA PenTest+ PT0-003 Official Guide – Wireless Reconnaissance Techniques

Configuring and Registering a Service:

Registering a malicious service ensures that it starts automatically with the system, providing persistence even after reboots.

This method is stealthier than others and is commonly used in advanced persistent threat (APT) scenarios.

Why Not Other Options?

B (Remote desktop software): Installing such software is noisy and can easily be detected by monitoring tools.

C (User logon script): While it provides persistence, it is less reliable and more detectable than a system service.

D (Kerberoasting): This is a credential-stealing technique and does not establish persistence.

CompTIA Pentest+ References:

Domain 3.0 (Attacks and Exploits)

Domain 4.0 (Penetration Testing Tools)