Top 10 High Impact Free and Open Source offensive tools

Whether you’re a seasoned red teamer or just diving into the world of offensive security, the right tools make all the difference. In this post, I will be highlighting 10 of the most impactful, easy-to-use, and completely free tools for testing the resilience of your environment. These are the same tools used in real-world penetration tests to uncover serious gaps before real attackers do. Bold notes indicate areas where something could potentially break!

All of these tools can be found or easily installed on any open source offensive distro like Kali linux or Parrot OS

1. Nmap — The Recon Workhorse

Nmap is the backbone of any solid assessment. This network scanner helps identify live hosts, open ports, and service versions across internal or external networks. It also includes a powerful scripting engine (NSE) that can detect known vulnerabilities.

Try this:

nmap -sC -sV -oA internal_scan 10.0.0.0/24

Run default scripts, version detection, and save results in multiple formats — perfect for recon at scale.

2. BloodHound — Map Your Path to Domain Admin

BloodHound uses graph theory to reveal hidden privilege escalation paths in Active Directory. It’s essential for visualizing attack paths based on group memberships, session data, ACLs, and more.

Collector example:

SharpHound.exe -c All

Import the results into the BloodHound GUI to identify routes to high-value targets like Domain Admins.

The Bloodhound Community Edition is free and the GUI is containerized.
https://bloodhound.specterops.io/get-started/quickstart/community-edition-quickstart

3. CrackMapExec — The Swiss Army Knife for Windows Networks

CrackMapExec (CME) is a post-exploitation favorite that lets you spray credentials, enumerate SMB shares, dump hashes, and even execute commands remotely. It’s built for speed and utility inside Windows domains. Be sure to limit your password guesses per account to something that is under your account lockout policy threshold!

Try a credential spray with a common password:

cme smb 10.0.0.0/24 -u users.txt -p Password123!

4. Impacket — The Backbone of Lateral Movement

Impacket is a Python toolkit that provides scripts to abuse common network protocols. Whether you’re dumping NTLM hashes, abusing Kerberos tickets, or remotely executing commands, Impacket is your go-to.

Dump hashes using:

secretsdump.py domain/user:password@10.0.0.5

5. Evil-WinRM — Seamless Shell Access on Windows

If WinRM is enabled and you’ve got credentials, Evil-WinRM gives you a powerful shell to the target system. It supports file upload/download, Powershell execution, and is ideal for post-exploitation.

Connect using:

evil-winrm -i 10.0.0.5 -u administrator -p 'P@ssw0rd!'

6. Responder — Easy Credential Capture

Responder listens for LLMNR and NetBIOS broadcasts on the network and tricks systems into sending their NTLM hashes. It’s highly effective on flat networks where name resolution is misconfigured.

Launch it with:

sudo responder -I <ethernet interface>

7. Burp Suite Community — Web App Hacking Made Easy

Burp is a staple for web application testing. The Community Edition is perfect for intercepting HTTP traffic, replaying requests, and manually testing web app logic — even without automation.

Setup Tip:
Install Burp, set your browser’s proxy to 127.0.0.1:8080, and start intercepting traffic for hands-on web testing.

8. LinPEAS / WinPEAS — Fast Privilege Esc Discovery

These scripts automate the search for local privilege escalation opportunities on Linux and Windows. They check permissions, kernel versions, SUID binaries, stored creds, and more.

On Linux:

wget https://github.com/carlospolop/PEASS-ng/releases/latest/download/linpeas.sh
chmod +x linpeas.sh && ./linpeas.sh

9. Ffuf — Blazing-Fast Web Fuzzer

Ffuf is a fast, lightweight tool for discovering hidden web directories, files, or parameters. It’s great for brute-forcing admin panels or probing API endpoints. I would reccomend testing this in QA / Dev environments first!

Discover hidden paths:

ffuf -u https://target.com/FUZZ -w /usr/share/wordlists/dirb/common.txt

10. Sliver — A Modern Open-Source C2 Framework

Sliver is a powerful command-and-control framework built in Go. It supports multiple operating systems, encrypted comms, and even team collaboration — a true open-source alternative to commercial C2s like Cobalt Strike. Hopefully the C2 Agent gets caught by your EDR or AV!

Generate an implant:

sliver-server
# then inside:
generate --os windows --format exe --listener http

Bonus!!! 11: Certipy — Weaponizing AD Certificate Services

Certipy is an incredibly powerful tool for identifying and exploiting misconfigurations in Active Directory Certificate Services (AD CS). AD CS is often overlooked during assessments, but when misconfigured, it can offer low-privileged users a fast track to domain admin — all through abused certificate templates and enrollment policies.

Certipy supports enumeration, request forgery, authentication relaying, and even domain persistence via certificate-based authentication. If AD CS is in play, this tool is a must-have in your arsenal.

Enumerate vulnerable templates:

certipy find -u 'user@domain.local' -p 'Password123!' -dc-ip 10.0.0.5

Request a certificate and impersonate a domain user:

certipy req -u 'user@domain.local' -p 'Password123!' -ca 'corp-CA\ca' -template 'VulnerableTemplate'

Use the certificate for authentication (pass-the-cert):

certipy auth -pfx user.pfx

The 11th tip is one that we abuse often during internal assessments and you might be surprised how often AD CS is not audited beforehand.

Hopefully these tools will prove useful for your internal security efforts. If a more thorough assessment feel free to reach out to us at help at adversaryacademy.com