If you manage any network infrastructure, port scanning should be a regular routine to lock things down. These invaluable tools detect open doors that hackers could exploit to infiltrate systems and steal data.
But between the technical jargon and scanner options available today, the concept can confuse beginners. As an experienced cybersecurity specialist, allow me to simplify everything you need to know in this beginner‘s guide.
We‘ll cover:
- What Exactly Port Scanners Do
- Why Port Scanning is Critical
- An Overview of How Scanners Work
- Common Types of Scans
- 10 Best Port Scanners of 2023
- Implementing Scans on Your Network
- Legal Considerations
- Other Scanner Fundamentals
So if terms like TCP, SYN, and ICMP scanning make your head spin, keep reading! This article will help demystify port scanning to leverage it protecting your infrastructure.
What Exactly Do Port Scanners Do?
First, let‘s explain port scanners at a basic level.
These tools survey your servers, workstations, networking equipment and other connected gear to see what communication "ports" are open. Think of an open port as an unlocked door into the device’s software and services.
Hackers search for these open ports as access points to break in and take control. Scanners find them first so you can shut access down.
Over 65% of network intrusions occur by exploiting application and service vulnerabilities through open ports. So locking things down is crucial.
Why is Port Scanning So Important?
Failing to scan networks allows weaknesses to linger. This gives attackers easy opportunities to infiltrate environments and wreak havoc.
Once inside, data theft, malware installation, resource hijacking for crypto mining, and system destruction are unfortunately common.
The stakes don‘t get higher than your company‘s sensitive information and infrastructure availability.
Ultimately, exploiting just a single open port can lead to over $4 million in damages on average from compromised intellectual property, recovery costs, and legal liabilities.
Routine scanning complements firewalls and other network security measures by checking for gaps. This proactive protection means finding and closing security holes before criminals infiltrate your digital perimeter.
How Do Port Scanning Tools Work?
Port scanners test network ports by sending specially formatted connection requests and analyzing the responses.
Each type of scanner works differently, but essentially they check whether the port:
- Successfully connects indicating an open port.
- Rejects access showing it‘s closed.
- Doesn’t respond meaning a firewall blocked the attempt.
By gathering this status information across all standard networking ports, security teams learn what needs to be closed to prevent unauthorized entry.
Now let’s cover some common scan types and tactics.
TCP Connect Scanning
The most definitive scan tries completing full TCP 3-way handshakes with each port, directly showing opened or closed.
TCP SYN Scanning
Sends a special TCP SYN packet and monitors responses to see if a port is listening and open. Fast without completing connections.
UDP Scanning
Sends UDP packets and watches for ICMP unreachable errors to detect closed ports or timeouts on open ports.
ICMP Scanning
Uses basic ICMP Echo Requests (pings) to map network topology and find devices prior to targeted port scans.
These and a handful of other scan types serve different purposes for flexibility meeting any needs on your network.
Ranking the Top 10 Port Scanners of 2023
With fundamentals covered, let‘s compare today‘s leading port scanning solutions. I evaluate scanners across dozens of criteria including:
- Scan accuracy and reliability identifying every open port
- Processing speed scanning thousands of ports per second
- Simplicity without needless complexity hampering usage
- Customization range allowing unique port and IP specifications
- Scalability for expanding networks with more devices
- Costs ranging from free open source to commercial suites
Based on extensive testing and expertise assisting clients, these rank as today‘s top port scanners to secure networks.
1. SolarWinds Port Scanner
SolarWinds tops my list thanks to its combination of power, flexibility and ease spanning networked environments. This scanner integrates with their advanced network monitoring software for unified visibility.
I appreciate the:
- Broad device support from servers to workstations and switches
- Preconfigured scans simplifying initial setup
- Custom port specifications so you scan just what’s necessary
- Processing speed up to 2000 ports per second for efficiency
- Detailed scan analysis reports
- Alert triggering linked to specific port conditions
- Intuitive web interface and mobile application controlling scans remotely
With a free trial available, paid licensing enables full functionality for continued usage beyond 14 days. Despite the cost, it’s by far my top choice for 2024 environments based on capabilities.
2. Nmap
Network admins working with Linux and open source solutions typically prefer Nmap for its excellent range of advanced scanning techniques. As a free and flexible cross-platform tool, highlights such as:
- NUMEROUS scan types from TCP SYN to UDP and ICMP
- Top-tier speeds up to 2000 pps rivaling paid counterparts
- Open source community providing ongoing support and script integrations
- Advanced users can customize scans through scripting
With no money down, Nmap empowers securing networks big or small without limits.
3. NetScanTools Pro
Optimized for surveying Microsoft centric environments, NetScanTools Pro delivers rapid vulnerability scanning alongside a loaded toolbox securing Windows infrastructure and troubleshooting.
I love how this scanner:
- Catalogues over 6100 common ports against Windows services for descriptiveness
- Controls scan scope with granular customization
- Schedules recurring scans through intuitive interface wizards
- Multi-thread searches for speed up to 1000 pps
- Integrates detailed reporting and file export capabilities
- Links to its database identifying mysterious processes binding to ports
Despite paid licensing, the combination of speed, usability and integrated toolset justify costs for many administrators overseeing Windows environments.
4. Angry IP Scanner
Don‘t let the name fool you – the Angry IP Scanner is a fast and friendly port scanner suitable for beginners through experts. Available across Windows, Mac and Linux, this open source tool performs at surprisingly high speeds lighter duty scanning.
- Easy-to-use graphical interface presenting functions via intuitive icons
- No programming knowledge needed for setup
- Quick processing topping 6400 packets per second
- Saves scanning reports in multiple formats like TXT, CSV, XML
- Supports direct IP address and domain name entry
- Subnet ranges preconfigured for single click convenience
- Configures custom port combinations for TCP, UDP scan blending
For lighter scans up to 10,000 ports on smaller networks, Angry IP brings respectable functionality completely free.
5. Advanced Port Scanner
Those overseeing single Windows workstations benefit from the Advanced Port Scanner bringing customizable professional-grade scans to local machines. Both freeware and paid Pro editions provide comparable core competencies:
- High speed processing outpacing native OS port tools tenfold
- Clean and simple interface without clutter
- Scan history tracking changes over time
- Powerful filtering of scan report data
- Export scanning in CSV or TXT formats
- Scanning and port listening specifics presented
- Configure custom protected ports lists exceptions
The commercial version extends adaptability with multithreading, priority adjusting, and advanced timeouts. With a $40 flat fee perpetual license cost, it’s a worthy scanner keeping individual Windows stations secure.
6. SoftPerfect Network Scanner
Don‘t let SoftPerfect Network Scanner’s bold “world’s fastest scanner” claim fool you – it‘s one fast search tool! On top of sheer speed, I appreciate how this scanner:
- Verifies open ports and maps network topology via TCP, UDP and ICMP scans
- Presents discoveries through a clean customizable interface
- Integrates with Active Directory for administrating Windows environments
- Exports intelligent scan reports in HTML, PDF, CSV and more
- Schedules recurring scans to track changes over time
- Provides a 30 day free trial period with no limitations
- Licenses affordably priced per administrator account needing access
For large enterprises and internal networks, SoftPerfect Network Scanner delivers thorough results with attractive licensing terms to match needs.
7. SolarWinds Engineer‘s Toolset
In the spirit of defense in layers, the SolarWinds Engineer‘s Toolset provides network detection capabilities alongside over 20 other security and infrastructure analysis tools. Compared to more dedicated scanners, it impresses by:
- Quickly surveying networks via IP sweep and port methods
- Identifying unknown processes binding to open ports
- Visualizing communications correlations between ports and programs
- Embedding scanning functions alongside numerous other network admin apps
- Granting 30-day free trials to experiment before buying
- Utilizing affordable network-wide licensing tiers
If you manage complex infrastructure supporting businesses, Engineer’s Toolset warrants your review delivering well-rounded IT monitoring.
8. PRTG Port Scanner
Already supporting large networks with device monitoring, PRTG’s integrated scanning combines responsive speed and customization for evolving landscapes. Consider that you can:
- Distribute scans across remote probes placed throughout infrastructure
- Schedule recurring scans feeding Always-on detection dashboards
- Configure custom alerts triggered by suspicious port activity
- Generate HTML, CSV and PDF formatted reports from anywhere
- Utilize flexible pricing based on monitored sensors versus strict device counts
As an alternative to isolated scanning tools, PRTG encompasses broader visibility with configurable audits keeping networks perpetually secure.
9. Port Scanner App
Last but not least, my top choice mobile port scanner goes to apps like Port Scanner by Vladimir Ivanov – downloaded over 1 million times!
Running natively on Android and iOS, this is my scanner recommendation for:
- Surveyors needing analysis on the go from client sites
- Quick convenience checks when tools aren’t installed locally
- Remote workers verifying home equipment protections
- IT teams lacking budgets for commercial packages
For under $4 paid, the feature capabilities and tool caliber defy expectations. Don’t underestimate on-phone solutions!
10. SocketGrab
Rounding out options, SocketGrab by Epsillion stands above other open source scanning platforms in the development arena.
I suggest SocketGrab for:
- Engineers needing added optimizations tailoring scans to your stack
- Developers integrating detections into broader software products
- Learning – study coding techniques advancing your career
With accessible C/C++ code repositories rather than precompiled binaries, opportunity abounds customizing SocketGrab to specific needs.
While requiring more involvement than turnkey tools, the open platform provides valuable foundations innovating as organizations mature.
This lineup provides a scanner suitable for any skill set and environment type. But don’t just take my word – try 2-4 options meeting your needs to make the best choice based on experience.
Implementing a Scanning Game Plan
While having the right scanner is step one, perfectly tuning scans to your infrastructure takes some trial and error. Follow my methodology to establish an effective port scanning game plan protecting your network.
Schedule Scans During Low Traffic Periods
Run scans outside high demand cycles minimizing disruption if ports go unresponsive. I recommend weekends or off-peak hours when most staff are logged out.
Stick to Non-Destructive Scan Types
Ping sweeps and TCP ACK scans simply query network state while SYN, UDP and Connect attempts alter flow. Pick scan types balancing visibility and system impact.
Define Scanning Frequency
I suggest scanning your full network weekly at minimum, while inspecting DMZ areas multiple times daily catching attacks faster. Know regulatory requirements as well influencing cadence.
Inspect Traffic Source Changes
Scanning also establishes baselines – so track where unfamiliar sending devices appear reaching corporate systems indicating backdoors.
Interpret, Assign and Respond to Results
Analyzing scan reports means nothing unless assigned to NOC teams closing vulnerable findings. Integrate with ticket workflows to drive remediation and policy actions neutralizing threats.
Are Port Scans Completely Legal? What About Ethics?
Understandably, using scans probative of networks prompts questions on legality and ethics.
- Port scanning itself remains broadly legal in most moderate regimes including the United States and United Kingdom when kept internal. Scanning with permission and for defensive cybersecurity purposes typically avoids allegations of computer hacking crimes should precautions be taken.
However, laws remain complex and situationally dependent:
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Scanning devices like medical equipment can still violate regulations like HIPAA protecting data.
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Scanning beyond firewall borders without permission raises legal concerns in some jurisdictions. Proceed carefully scanning third parties externally.
My recommendations minimizing ethical and legal pitfalls:
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Seek written consent where possible when scanning beyond owned assets.
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Provide prior written notice even for internal scans ensuring availability impacts get documented.
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Never attempt to conceal identity or exploit vulnerabilities found. Discovery must avoid disruptive denial of service to uphold standards.
Overall, ensure you operate carefully within reasonable security research boundaries rather than seeking overt technical system compromise without cause.
Other Scanner Considerations and Best Practices
Beyond core functionality, keep these other aspects in mind selecting and implementing your port scanning defense:
Combine Scanning With Broader Monitoring
Port scans provide just one snapshot of network health. For full protection, integrate scans feeding continuous monitoring tools tracking all device activity in real time. This ensures gapless visibility into abnormalities that scans may miss in between.
Use Scans Supporting Compliance Mandates
Regulations like PCI DSS require demonstrating vulnerability management protections for enterprises transacting payments. Leverage scans assisting documentation of formalized audits meeting these infosec obligations.
Consider Remote Access Scanning
In remote work environments, endpoint agents can scan home network equipment for gaps protecting corporate access. Confirm VPNs and backhaul equipment stay patched blocking intrusions from afar.
Enable Change Tracking
Compare periodic scans tracking fluctuations in open ports and listening services. New openings prompt investigation ensuring rogue applications don’t bypass oversight introducing risk.
Practice Prudent Scan Sharing
Be cautious sharing detailed reports indicating infrastructure layouts and weaknesses without vetting recipients. Sanitize reports before release avoiding supporting reconnaissance for would-be attackers.
Supplement With Manual Testing
Despite accuracy improving among scanners, still manually validate detected ports using telnet, netcat or other verification tools guaranteeing findings. Automation helps efficiency but shouldn’t replace hands-on scrutiny.
Conclusion
With attackers aggressively probing defenses for any openings, leveraging port scans remains crucial preventing network infiltrations before they occur.
Carefully implement recurring scans tuned to your environment, while closing any discovered ports allowing unneeded access. As threats evolve, adapt your game plan maintaining secure configurations.
By putting this guidance into practice alongside the other tips covered today, you can lock intruders out of infrastructure keeping invaluable data and services safe from compromise.
Here‘s wishing you strong cybersecurity fortifying your company through proper port scanning! Please don’t hesitate to reach out with any questions arising executing your program.