Vulnerability scanning is the process of searching for known security flaws in your network. It’s a regular health check-up, but for your digital infrastructure. These flaws could be anything from outdated software to misconfigured settings. 

The goal of vulnerability scanning is to catch any weaknesses before they turn into full-blown issues, before bad actors have a chance to exploit them. For example, you might find an old version of a web server running that's susceptible to known exploits. 

What does vulnerability scanning entail?

There are tools used to scan computer systems and networks for vulnerabilities. These tools go through your network with a fine-tooth comb, identifying any potential security risks. They scan various components—servers, endpoints, firewalls, and even IoT devices. 

Once the scan is complete, these tools generate detailed reports highlighting the issues found, often along with suggestions for fixing them.

To protect your company networks against old, new, and emerging security threats, you must schedule vulnerability scans regularly, say once a month, and after any major changes to our network. 

When you deploy a new server or apply significant updates, it’s crucial to run a scan. This helps ensure nothing new has inadvertently introduced a vulnerability. For instance, if you roll out a new customer-facing application, you would immediately scan to make sure there are no entry points for attackers.

It’s also a security best practice to prioritize the vulnerabilities found. Not all issues need to be fixed immediately. Some might only pose minor risks, while others could be serious threats. 

To determine the severity of vulnerabilities, you we use the Common Vulnerability Scoring System (CVSS). A critical vulnerability, like one allowing remote code execution, would be at the top of your to-do list. On the other hand, a minor misconfiguration might be scheduled for a routine maintenance window.

It's important to note that vulnerability scanning is not a one-time task but an ongoing process. The threat landscape is constantly evolving, and so must your defenses. 

By making vulnerability scanning a regular practice, you keep your company's digital assets much safer from potential threats.

Automated vs. manual scanning

When it comes to vulnerability scanning, there are two main approaches: automated and manual. Each has its own strengths and weaknesses, and the best choice often depends on the specific needs of your company's network.

Automated scanning is, as the name suggests, handled by software tools that scan your network for known vulnerabilities. These tools are incredibly efficient at covering a lot of ground in a very short amount of time. 

For example, an automated tool can scan thousands of endpoints overnight and provide you a report first thing in the morning. The speed and breadth are invaluable, especially for large networks. 

Tools like Nessus or OpenVAS are popular choices. They can detect everything from outdated software to improper configurations.

However, automated scanning isn't perfect. These tools rely on predefined databases of known vulnerabilities. If a new vulnerability has just been discovered and hasn't made it into the database yet, the automated scanner might miss it. 

Moreover, automated tools can sometimes generate false positives—alerting you to vulnerabilities that aren't actually there. This can create extra work as you verify each supposed issue.

On the other hand, manual scanning involves a security professional going through your network, often with the aid of specialized tools but using their own expertise to find potential vulnerabilities. This method is slower and requires more resources, but it can uncover issues that automated tools miss. 

For instance, a skilled security expert might notice a subtle misconfiguration that an automated scanner would overlook. Manual scanning is also better at understanding the context of your specific network, which can result in more accurate results.

Say you have a custom-built application running on your network. Automated tools might not completely understand the intricacies of this application. During a manual scan, a security expert can interact with the application directly, test different inputs, and analyze its behavior in ways that automated tools can't mimic.

In practice, the best approach often involves a combination of both automated and manual scanning. You can leverage automated tools to continuously monitor your network and perform regular, broad scans. Then, you can follow up with targeted manual scans, focusing on the most critical assets or any areas flagged by the automated tools.

By blending both methods, you take advantage of the speed and efficiency of automation while still applying the detailed, nuanced understanding that only human expertise can provide. This ensures that your network remains as secure as possible against a wide range of potential threats.

Common types of vulnerabilities

Software bugs

Software bugs are errors or flaws in your software applications that could be exploited by attackers. For instance, think about the infamous Heartbleed bug. It was a vulnerability in the OpenSSL cryptographic library that allowed attackers to read sensitive information from affected systems' memory. That’s a classic example of a software bug turning into a potential nightmare.

Misconfigurations

Misconfigurations occur when systems or applications are not set up correctly, leaving doors open for unauthorized access. A simple example is an unsecured database. 

A database without proper authentication settings opens a door to all manner of attacks. Anyone could potentially access it and retrieve confidential data. This kind of oversight can lead to serious breaches.

Weak passwords

Guessable passwords are a major vulnerability you must watch out for during your scans. Despite frequent warnings, it's not uncommon to find passwords like "123456" or "password" still in use. 

Such passwords are extremely easy for attackers to guess using brute force attacks. It’s crucial to enforce strong password policies to mitigate this risk.

Outdated software

When software isn't updated regularly, it misses out on critical security patches. An outdated web browser or operating system can be particularly vulnerable. 

For example, continuing to use an old version of Windows that Microsoft no longer supports can leave systems exposed to known exploits.

Another sneaky type of vulnerability involves third-party software. Many of us rely on third-party components or libraries, and if these aren't kept up-to-date, they can introduce vulnerabilities into our systems. 

Take the Apache Struts vulnerability that led to the Equifax breach, for instance. That was a third-party software issue that had massive ramifications.

Unprotected default settings

Many devices and applications come with default configurations that are far from secure. Leaving these unchanged leaves your systems open to attacks. 

For example, some routers come with a default admin password like "admin" or "password" that users never change. This makes it exceedingly simple for an attacker to gain access.

So, while running vulnerability scans, you must keep an eye out for these common types of vulnerabilities. Catching these early can save you from a lot of headaches down the road.

Vulnerability scanning methods

Network-based vulnerability scanning

Network-based vulnerability scanning is all about detecting weaknesses in the devices and services connected to your company’s network.

When you start a network-based vulnerability scan, you are essentially mapping out your entire network. This includes identifying all the devices—servers, routers, switches, and even the sneaky IoT gadgets that sometimes slip through the cracks. 

Once you have got this map, the scanner probes each device, looking for open ports, active services, and any outdated software versions. For instance, if you still have devices running older versions of Windows Server, the scanner will flag this as a potential risk due to known vulnerabilities in those versions.

It's worth pointing out that network-based scans can sometimes destabilize your network. If the scans are too aggressive, they might slow down or even disrupt some services. 

So, you can run these scans during off-peak hours and tweak the scan settings to balance thoroughness with caution. For example, you can start with a less intrusive scan to identify the most glaring vulnerabilities and then run more detailed scans as needed.

Host-based vulnerability scanning

Instead of scanning the entire network, host-based vulnerability scanning zeroes in on individual devices—like servers, workstations, or even specialized equipment like IoT devices. This type of scanning is crucial because it provides a deep dive into the vulnerabilities specific to each host.

If you’ve got a server running critical applications, a host-based scan will meticulously inspect this server’s operating system, installed software, and configurations. 

So, if your server is running an outdated version of a web server software, the scan might reveal a known vulnerability, suggesting an urgent patch to avoid exploitation.

You can run these scans either from the host itself or remotely. Tools that sit on the host, continuously monitor for vulnerabilities, checking for things like missing patches, weak passwords, or misconfigurations. 

If there’s an issue, the tool will flag it right away. This proactive approach means you are not waiting for an attacker to find a weakness first.

One of the big advantages of host-based vulnerability scanning is its granularity. When scanning an individual machine, you capture nuances that might get missed in a broader network scan.

For instance, a host-based scan might uncover a specific application vulnerability on a database server that a network scan would overlook. It's like having a microscope instead of a magnifying glass.

You can also leverage host-based scans for compliance purposes. Regulations like PCI-DSS or HIPAA often require regular scans of key systems. Host-based vulnerability scanning allows you to generate detailed reports, showing regulators that you are diligently keeping your systems secure.

But it’s not just about finding vulnerabilities. Host-based scans are great for verifying security policies. If you have set a policy that all systems must use complex passwords, a scan can quickly show you which hosts aren’t complying.

In short, host-based vulnerability scanning zeroes in on the minute details of each host, ensuring you catch vulnerabilities and enforcement gaps that could otherwise slip through the cracks. 

Cloud-based vulnerability scanning

Cloud-based vulnerability scanning identifies weaknesses in cloud-hosted services and internet-facing systems. 

One of its benefits is convenience. You don't need to worry about updating scanners or managing the infrastructure. Providers handle all of that for you. Their tools continuously monitor your systems, sending alerts if something needs your attention.

Cloud-based vulnerability scanning also adapts to complex and distributed networks. If your company has several branches globally, scanning all of them with traditional tools would be a logistical nightmare. But with cloud solutions, you can ensure every branch is covered without any extra effort. 

AWS Inspector, for example, integrates directly with AWS services. It automatically assesses your EC2 instances for vulnerabilities and deviations from best practices. You get a detailed report without any manual interventions.

Collaboration is also easier with cloud-based scans. Multiple teams can access the scanning reports and dashboards from anywhere. Any team member can log in and view the latest results, ensuring everyone stays on the same page. This is perfect for remote or hybrid work environments.

Many cloud vulnerability scanning solutions integrate seamlessly with other security tools you might be using. For instance, integrating a cloud scanner with your SIEM system can automate threat detection and response. 

Cloud-based vulnerability scanners are also easy to scale. They grow with your network and the evolving threat landscape. 

As your company grows, your vulnerability scanning needs will grow too. Traditional scanners might struggle with this, but cloud-based ones do not. They can scale up or down based on your requirements. 

Take Microsoft Defender for Cloud as an example. It can protect everything from small virtual machines to large microservices architectures without any hiccups.

In essence, cloud-based vulnerability scanning transforms how you protect your networks. It’s efficient, adaptable, and perfect for modern-day needs. By leveraging these tools, you can ensure your defenses are always up-to-date, no matter where your operations take you.

Wireless vulnerability scanning

Wireless vulnerability scanning your Wi-Fi for vulnerabilities. It looks for issues like rogue access points, which are unauthorized devices broadcasting Wi-Fi signals in your environment. 

An example is someone setting up a Wi-Fi hotspot in your office without permission. An attacker could do this to trick your employees into connecting to a malicious network. There are tools that sniff out these rogue access points quickly.

Another thing to watch out for is weak encryption protocols. You remember the old WEP encryption? It's not secure. We must use WPA3, the latest and most secure protocol. 

During a scan, you can check if any parts of your network are still using outdated encryption. It's like ensuring all your doors are locked with high-quality deadbolts.

Then there's the issue of default settings. Many access points come with default configurations that are easy for attackers to exploit. You should make it a point to ensure that all factory and common default settings have been changed.

SSID broadcasting is another element to consider. Broadcasting your network name can sometimes be necessary, but it also makes it easier for unauthorized users to find us. If a network doesn't need to be visible, disable SSID broadcasting.

Lastly, pay attention to signal leakage. Letting your Wi-Fi signals extend beyond the physical boundaries of your office building could allow people in the parking lot, for example, to try and gain access. You can use a wireless sniffer to measure how far your signal reaches and adjust the access point settings to limit this reach.

Scanning applications for vulnerabilities

Scanning applications for vulnerabilities involves using automated tools to check web applications for security issues. These scanners help find vulnerabilities like: 

• cross-site scripting (XSS), 
• SQL injection, and 
• insecure server configuration. 

For instance, they can detect XSS by sending HTML test strings and looking for these strings in the responses. A good example of an app scanner is OWASP's Zed Attack Proxy (ZAP), known for its efficiency in finding web application vulnerabilities.

Different application scanners have varying capabilities. Some are more advanced and can discover complex issues. For example, Burp Suite Professional is excellent for identifying vulnerabilities that many other tools might miss. 

Burp Suite Professional uses advanced techniques to uncover asynchronous SQL injections and blind SSRF vulnerabilities. This scanner is particularly useful because it delves deeper into the application, providing thorough security checks.

These scanners used to scan web applications are known as Dynamic Application Security Testing (DAST) tools. They operate by simulating real-world attacks to identify potential security threats. 

It's crucial to know that while these tools are powerful, they sometimes produce false positives. This means not every vulnerability they identify is necessarily a threat. Some of their findings might need manual verification.

Therefore, using application scanning tools effectively requires understanding their strengths and limitations. Some of them allow you to customize your scans based on specific needs. For example, you can configure them to focus on certain types of vulnerabilities or to run more detailed scans on high-risk areas of your application.

The vulnerability scanning process (discovery, enumeration, vulnerability detection)

Stage 1 - Discovery

This is where you figure out which devices are active on your network. Your scanner of choice can use different host discovery techniques, like quick ARP requests or more detailed TCP and ICMP probes. 

For instance, you might start with something like an `-sn` option to just ping the network range and identify live hosts. It's a quick way to see who's home.

Stage 2 - Enumeration

In this stage, your scanner digs deeper into the specifics of each active host. It starts by resolving DNS names for better readability. 

An IP address doesn’t tell you much, but a hostname can give hints about a device's role. That's why you must use the `-sL` option for a list scan with no resolution or `-R` for resolving all IPs. This step can't be skipped because it's crucial for identifying your targets and narrowing down the focus.

Stage 3 - Port scanning

Here, your scanner sends probes to various ports to figure out which ones are open, closed, or filtered. You can use a SYN scan (`-sS`), which is quick and less likely to be noticed by firewalls. You are essentially sending requests to different network ports and seeing which ones respond.

But it doesn’t stop there. If you find any open ports, you can ramp things up with version detection using the `-sV` option. This tells you what software is running on those ports. Your scanner sends various probes and matches the responses against its vast database of service signatures.

Then there's OS detection, triggered with the `-O` option. Different operating systems respond in their own peculiar ways to network probes. Most scanners match these quirks to its database of known OS fingerprints. Knowing the OS can be a big advantage, especially when looking for vulnerabilities specific to that system.

Stage 4 - Vulnerability detection

At this point, you will configure your scanner for vulnerability detection. By using the `--script` or `-sC` options, Nmap, for example, runs scripts that check for known vulnerabilities, malware, or deeper service details. For example, there’s the `vuln` script category which can reveal a lot about the security posture of the network. 

Stage 5 - Output

Here, all the data collected is neatly arranged for analysis. Nmap can display the results in a human-readable format right on my screen or save it in various formats like XML. This lets you see at a glance what's going on with the network and where the vulnerabilities lie.

Common tools and software used in (e.g., Nessus, OpenVAS, Qualys) - Vulnerability Scanning

There are several tools and software available on the market that you can use to scan your network and systems for vulnerabilities. Names like Nessus, OpenVAS, and Qualys come to mind. Each has its unique strengths, and depending on your needs, one might be better suited for your company than another.

Developed by Tenable, Nessus is a fantastic tool that's incredibly thorough in its scans. From misconfigured firewalls to outdated software, the scanner covers all bases. 

Desired for its ease of use, Nassus has an intuitive dashboard and takes just a few clicks to set up a scan. Plus, its detailed reports make it easy to understand the risks and prioritize fixes.

OpenVAS, on the other hand, is an open-source alternative that packs a punch. It's free yet powerful. Being part of the Greenbone Vulnerability Manager, it provides comprehensive scanning that rivals many paid solutions.

The community support around OpenVAS is excellent, too. You can rely on the helpful forums when you run into problems. The only downside might be the setup that’s a bit more complex compared to Nessus. But once you get it up and running, it's a formidable ally in network security.

Then there's Qualys, a cloud-based scanner that is a favorite among larger enterprises. What sets Qualys apart is its scalability. Whether you're a small business or a giant corporation, Qualys can handle the load. 

Qualys’ integration capabilities are worth pointing out. It’s fairly straightforward to hook it up with your existing SIEM) systems. Another major plus is its asset management feature. Knowing exactly what devices are on your network is half the battle, and Qualys does a stellar job at it.