Simulating Attacks: Real-World Exploitation in Network VAPT
A network penetration test (network VAPT) checks whether weaknesses in your network can actually be used to gain access. Six that testers commonly check are weak SNMP settings, ARP spoofing, easy lateral movement, DNS cache poisoning, default credentials and outdated firmware. This guide explains what each one is, why it matters and how to fix it. Test only networks you own or have written permission to test.
Networks grow over time. Old devices stay in service, settings are left at their defaults, and flat layouts let one compromised device reach many others. A penetration test shows which of these gaps are real in your environment so you can fix them in order of importance.
This guide is written for defenders. It explains weaknesses and fixes, not how to attack a network.
How a Network Test Works
The NIST SP 800-115 technical guide to security testing describes four phases: planning, discovery, attack and reporting. Planning sets scope, rules and permissions. Discovery finds systems and weaknesses. The attack phase checks which weaknesses can be used. Reporting records findings and fixes. NIST also warns that testing can damage systems, and that crafted network traffic can cause denial of service, so testing windows, stop rules and rollback plans should be agreed first.
Planning
Written scope, permissions, test windows and a named contact on your side.
Discovery
Finding devices, services and settings, then listing possible weaknesses.
Confirming findings
Manual checks, agreed beforehand, to show which weaknesses can really be used.
Reporting and retest
Plain-language findings with fixes, then a retest to confirm they worked.
Severity scores such as CVSS describe how serious a flaw is in general. They do not describe the risk to your organisation, so consider what each system holds and who can reach it.
Six Common Weaknesses and How to Fix Them
Each card below says what the weakness is, why it matters and what to do about it.
1. Weak SNMP settings
SNMP lets management systems read from and manage network devices. Community strings work like passwords, and the Cisco IOS XE hardening guide says they should be non-trivial and changed at regular intervals. Easily guessed strings can expose device information, and read-write access can allow changes.
Fix: If SNMP is needed, use SNMPv3 and allow access only from approved management systems, and disable other versions, as the ASD edge device guidance advises. If it is not needed, turn it off.
2. ARP spoofing
ARP maps IP addresses to hardware addresses on a local network, and it has no authentication. As Cisco documents, forged replies can poison ARP caches so traffic passes through the wrong device. The attacker needs to be on the same local network segment first, so this is a risk after another weakness has already been used.
Fix: Enable Dynamic ARP Inspection on switches where supported. It checks ARP packets against known address bindings, relies on DHCP snooping or ARP access lists, and only protects hosts on switches that run it. Keep user and guest networks separate from servers.
3. Easy lateral movement
Once one device is compromised, a flat network lets it reach many others. CISA, NSA and partner agencies list lack of network segmentation, improper separation of user and administrator privilege, and insufficient internal monitoring among the top ten misconfigurations in a joint advisory.
Fix: Segment the network with filtering rules to contain breaches and limit lateral movement, as the ASD guidance describes. Give accounts only the access they need, keep administrator accounts separate, and send logs to a central system so unusual activity is noticed.
4. DNS cache poisoning
Attackers can send forged DNS responses so users are redirected to sites they control. ICANN says DNSSEC is designed to ensure DNS content cannot be modified from its source without being detected, by signing records.
Fix: Sign your domains with DNSSEC and use resolvers that validate it. ICANN says the full benefit needs support along the whole chain, including domain owners and internet providers. DNSSEC checks authenticity and does not encrypt DNS traffic. Keep DNS servers patched and logged.
5. Default credentials
Devices often ship with vendor passwords that are publicly known. The CISA advisory lists default configurations of software and applications first among the top ten misconfigurations, and default credentials are part of that item.
Fix: Change default accounts and credentials at setup, audit existing devices for defaults, and prefer products that make you create credentials, as the ASD guidance advises. Add multi-factor authentication for management access where supported.
6. Outdated firmware
Vendors stop issuing security updates when a device reaches end of life. The ASD guidance says edge devices that have reached end of life are particularly vulnerable, and that applying a patch will not fix a device that is already compromised.
Fix: Keep an inventory of devices and firmware versions, apply vendor patches on a schedule, and replace unsupported devices. The ASD guidance recommends replacing them immediately, or, where that is not possible, assessing the risk, adding compensating controls and setting a replacement date.
Fixes can interrupt service, so plan changes for approved maintenance windows and keep a way to roll back.
Fix-First Checklist
Use this table to turn findings into actions. Order the work by the importance of the systems affected, not only by score.
| Weakness | First action | Then |
|---|---|---|
| Weak SNMP | Find devices that still use SNMP and disable it where unused. | Move the rest to SNMPv3 and limit access to approved management systems. |
| ARP spoofing | Separate user, guest and server networks. | Enable Dynamic ARP Inspection with DHCP snooping on supported switches. |
| Lateral movement | List which systems can reach which, and remove access that is not needed. | Segment the network, separate admin accounts and centralise logs. |
| DNS cache poisoning | Check whether your domains are signed and your resolvers validate. | Keep DNS servers patched and review their logs. |
| Default credentials | Audit devices for vendor defaults. | Change them, enable multi-factor authentication where supported and add checks to device setup. |
| Outdated firmware | Build a device and firmware inventory. | Patch on a schedule, replace unsupported devices and retest. |
After fixing, ask the tester to retest. This confirms the fixes worked and have not created new problems.
Content Reviewed By
Ketki Tidke
Cyber Security and GRC Lead Auditor
ISO 27001 Lead Auditor
Ketki is a certified ISO 27001 Lead Auditor specialised in Governance, Risk and Compliance, with experience consulting public, private, and government clients. She evaluates threats, risk impacts, and regulatory requirements across multiple industry frameworks.
Network VAPT Weaknesses: Frequently Asked Questions
What is network VAPT?
Network VAPT is vulnerability assessment and penetration testing of a network. The assessment lists weaknesses, and the penetration test adds manual work to show which ones can be used in practice. Both are done with written permission.
Why do testers check SNMP?
SNMP is used to manage network devices, and weak community strings can expose device information. Guidance from the Australian Signals Directorate advises using SNMPv3, allowing access only from approved endpoints and disabling other versions.
What is ARP spoofing?
ARP maps IP addresses to hardware addresses on a local network and has no authentication, so forged replies can mislead other devices. An attacker needs to be on the same local network first. Dynamic ARP Inspection on switches is one control.
What is lateral movement?
It is movement from one compromised device to others on the same network. Segmentation, least privilege and central logging help contain it.
Does DNSSEC encrypt DNS traffic?
No. According to ICANN, DNSSEC signs DNS records so changes can be detected. It checks authenticity and integrity, and its full benefit needs support along the whole chain.
Why are default credentials a problem?
Vendor default passwords are widely known. A joint advisory by CISA and NSA lists default configurations of software and applications first among the top ten misconfigurations. Change defaults at setup and audit existing devices.
What should we do with devices that no longer get updates?
Guidance from the Australian Signals Directorate recommends replacing end-of-life edge devices immediately. If that is not possible, assess the risk, add compensating controls and set a replacement schedule.
Can a penetration test damage my network?
It can if it is not planned. NIST SP 800-115 warns that testing can damage systems. Agree the scope, test windows, stop rules and rollback plans in writing before work starts.
Is this the same as a vulnerability scan?
No. A scan uses tools to list possible weaknesses. A penetration test adds manual work to confirm which weaknesses can be used and what they would give an attacker.
How often should we test?
The sources we reviewed give no single interval for everyone. Test regularly and after major changes, such as new devices or network redesign, unless a rule that applies to you sets a schedule.
How do we get started?
List your network devices and where sensitive systems sit, agree what is in and out of scope, and ask providers for a written scope and quote. CyberSapiens can help you plan this.
Need a Network Penetration Test?
Talk to CyberSapiens about your network, scope and goals. We will help you decide what to test first and how to plan it safely.
Email us
[email protected]Our head office
Lvl 1 206 Lorimer St, Port Melbourne, 3207
