Introduction to auditing network services
You learn ports and services as the doors of a building, see the services listening on your machine and the lab network, audit common services, switch off the needless ones and verify from outside that they are closed.
Level 101 · 15 lessons · 15 practice labs
Lessons
What a service is
- Ports and services: the doors and staff of a building
- The service banner: how a service introduces itself
- Seeing the services listening on your machine: ss and netstat
- Needed or not: the purpose of a service inventory
- Short task: list the services listening on your lab machine and justify each one
Getting to know common services
- FTP: auditing anonymous login
- SSH: seeing the version and authentication methods
- HTTP: headers, the default page and version information
- SMB: listing shares and auditing guest access
- DNS: checking whether the server answers everyone
- Short task: audit five services and write one recommendation for each
Closing
- Stopping a needless service and keeping it from starting at boot
- Opening a needed service only to the network that needs it
- Verifying from outside that it is closed
- Capstone: audit, reduce and verify the services of a lab server
Practice labs
- List and justify the services listening on your lab machine: List the listening ports and processes with ss and write in one sentence whether each is needed.
- Bind a service listening on all interfaces to localhost: Find the database that should be local-only listening on all interfaces, bind it to localhost and verify it is unreachable from outside.
- Identify an unknown listening process and decide on it: Identify the process listening on an unknown port on Tarçınlı Fırın's server via its package, service unit and file path, and document the removal decision.
- Read three service banners and note the versions: Connect to the FTP, SSH and mail services with netcat and record the software and version from their banners in the inventory.
- Remove version information from service banners: Turn off version display in the web and FTP service configurations and reconnect to verify the banners are trimmed.
- Compare the banner version with the installed package: Compare the banner version with the installed package version on Narçiçeği Eczaneleri's server, find the cause of the mismatch and fix the inventory.
- Check and disable anonymous FTP login: Test whether anonymous login is enabled on the lab FTP server, disable it in the configuration if so and test again.
- Audit the SSH server's authentication methods: View the SSH version and offered authentication methods from outside, disable password login and verify key-only access.
- Audit five services and write one recommendation each: Audit the FTP, SSH, HTTP, SMB and DNS services on Kumsal Turizm's server and write a justified fix recommendation for each.
- List SMB shares and check guest access: List the shares on the lab file server and tabulate which ones are reachable without credentials.
- Check whether the DNS server answers everyone: Test whether the lab DNS server answers recursive queries from the outside network and limit it to the internal network.
- Close the SMB and DNS gaps and re-verify from outside: Close the guest share and open recursion on Gelincik Okulları's server and prove both fixes by testing from the outside network.
- Stop an unnecessary service and prevent it starting at boot: Stop the unnecessary print service on the lab server, disable it at boot and show it stays off after a reboot.
- Open a needed service only to the network that needs it: Open the management interface only to the management subnet with the firewall and scan from another subnet to verify it is closed.
- Audit, reduce and verify a lab server's services: Audit every service on Mavikaya Lojistik's warehouse server, disable what is not needed, narrow the rest and report with a before-and-after scan comparison.
About this course
You learn ports and services as the doors of a building, see the services listening on your machine and the lab network, audit common services, switch off the needless ones and verify from outside that they are closed.
What you will learn
- What a service is
- Getting to know common services
- Closing
Prerequisites
No prior knowledge is needed; the course starts from zero.
Lab environment
Lessons run in your own Kali Linux terminal in the browser, connected to a private lab network. Nothing to install.
Frequently asked questions
- Is this course right for my level?
- The course is at beginner level; every term is explained where it first appears.
- Is there anything to install?
- No. Every lesson runs in your own lab environment that opens in the browser.
- How do lessons work?
- Each lesson has 8 to 10 steps and a short quiz. Early steps show the command to type, later steps give less help; if two attempts fail, the solution opens.
- Can I try it for free?
- Yes. The first three lessons of every course are free.