How to reduce the digital risks of remote working, including the red team experience of Product Lead, Andy Hornegold.
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How to build a resilient remote-working business

James Harrison

Whether business owners like it or not, remote working is here to stay. About 42% of workers already work a remote or hybrid schedule, according to a Gallup study. Some head into the office for team meetings and face-to-face collaboration, but many work from home all week – wherever that may be – allowing for a truly global and dispersed workforce. We all know the pros and cons by now, but here we’re going to focus on one downside in particular: it’s harder to manage, monitor and secure IT.

Laptops and smartphones blur the lines between work and play. Workers answer Slack messages, send emails and access sensitive company information from their devices on the go, and outside the corporate network. This compromises every organization's security. So let’s look into the risks of remote working – and what you can do to reduce them.

How does remote working impact cybersecurity?

The shift to remote work was well underway before the pandemic, but IT teams had to work round the clock to enable employees to stay connected, collaborate and productive when COVID hit – by whatever means possible.

The first priority was to maintain business continuity, and security often took a back seat – opening businesses to a host of potential security vulnerabilities. Many relied on tried and trusted remote access solutions like VPNs; some invested in virtualization and DaaS services; others ignored security altogether and fell back on old, unpatched legacy equipment. The result? Their attack surface expanded exponentially and left them dangerously exposed.

What are the common risks of remote working?  

What’s wrong with relying on a VPN?

Many relied on tried and trusted VPNs to connect their teams to their company network. A VPN acts as an intermediary between the user getting online and connecting to the internet by hiding their IP address.

VPN’s themselves aren’t the problem, but they can only handle so much traffic. With the massive increase in traffic with everyone working from home, many fell back on the "split tunnel" configuration of their VPN clients.

This meant traffic went through the VPN to connect to the company network, but when they searched Google, checked LinkedIn or streamed YouTube, traffic would bypass the VPN and use the employee’s home network instead. This one single configuration change meant businesses no longer had control over what their employees could connect to, download or access. But what did this mean in practice?

Experience: existing technology (mis)handles new requirements

By Product Lead, Andy Hornegold

When systems/workstations are contained within an internal network you can restrict what those systems can connect to – everything crosses your businesses internet boundary. For example, you can stop connections to the internet over the file share functionality embedded in Windows (SMB). Almost every organization will restrict access from their internal network to the internet using SMB – there are very few use cases where it’s a good idea to allow it.

When people started working from home, many used laptops with a VPN to connect to and sent traffic via the business's network. This meant that every time the laptop tried to connect to a business system, the traffic would go via the VPN to the business network; but every time they connected to a non-business system the traffic would connect over the user’s home network. With this one configuration change, the business now no longer controls what the laptops can connect to and security has become a little more porous.

I was running red teams when this was happening. We phished a user and accessed a single laptop with endpoint security. It had a VPN into the company network which was locked down, but the VPN was running in split-tunnel mode so the laptop could connect to the internet. We couldn’t do much without being detected, but we could look through one of the business’s file shares the user connected to.

We dropped a simple .url file in a directory on the company file share, and it was a directory used by all employees. When you browse your filesystem and come across a .url, Windows Explorer will try and show an icon for that file, and the location of the icon is specified within the .url file itself. We specified that the icon was stored on an internet server which we controlled.

Now, every time an employee browsed to that file share, their Windows OS would send a request to our server for the icon so that it can display in Explorer. When our server asked the victim’s Windows OS to authenticate in order the retrieve the icon, it sent the hashed credentials of the victim user to us. We could crack those hashes and use them to access other internal systems and internet-facing systems with the same credentials.

The universal advice for this issue is to “block SMB connections to the internet at your firewall”. But this doesn’t work when people are working from home, because the connection doesn’t come from the business network. We exploited this daily to hoover up credentials from users across the business.

This is a really simple technique, and it shows how businesses risk profiles have fundamentally changed because of the new ways of working.

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This shows how a single configuration change can mean that IT teams no longer have control and visibility of what their people are using and connecting to. And if you can only get security updates when physically in the office, your team won’t get them while working from home.  

If your threat detection software is network-based, it’s ineffective when no one is actually on the office network. This might be manageable when your team is hybrid and comes into the office once a week, but not when they’re fully remote. And unpatched software is one of the most common breaches.  

This is why zero-trust is so prevalent today. With zero trust, there are no boundaries and no perimeter. No one is inherently trusted. Everything is compartmentalized, and there is security in isolation. While it’s more restrictive, the benefit is that it creates a far more secure environment that provides better protection against unauthorized access.

So what makes a resilient business?

Ask yourself – what if? What if you're hacked and lose control of your systems and data? How will it impact your business? Would you lose your customers? Would you lose your reputation? Could you be hit with a fine? If the answer is yes to any of these, then it’s time to take your cybersecurity more seriously.

It’s natural that smaller businesses focus more on their bottom line than potential risks. But there are simple measures you can put in place now to safeguard your systems – whatever the size of your business. Vulnerability management, multi-factor authentication on every login, backing up your data, and using a password manager – these are just some of the basics that every business – however big or small – should put in place.  

But it’s also important to understand that even with these precautions and a zero trust approach, you can still fall victim to hackers. That’s why you need to prepare for the worst and make sure you have a robust risk management and business continuity plan in place. Put simply, will your business survive if you’re hacked? If not, how could you be more resilient?

Absolute or relative?

There’s no single definition of what makes a resilient business. It depends on what type of organisation you are, how fast you’re growing and scaling, what industry you’re operating in, who you're trying to keep out, and what scenarios you want to resist. For example, healthcare and financial services providers need robust cyber security because they hold sensitive customer data and both industries are tightly regulated.  

But even in these scenarios, ‘absolute resilience’ is almost impossible and probably not worth the time, effort and expense. A more realistic approach is to aim for what you are willing to accept as a business. Choose what resilience looks like to you, and you can reach this ‘relative resilience’ with a few simple tips.

9 top tips to become more resilient  

  1. Don’t work on personal devices
  1. Don’t download unapproved software
  1. Keep your software updated
  1. Secure remote access with a VPN
  1. Secure sensitive data stores and ensure they’re backed up frequently
  1. Monitor your network to see what's exposed to the internet
  1. Regularly check for vulnerabilities and fix them promptly
  1. Implement Multi-Factor Authentication (MFA) everywhere
  1. Train your team to follow cyber security best practices

How Intruder can help boost your resilience

While these steps are easy to implement, keeping track of all activity on your network and changes to your cloud accounts isn’t a walk in the park. But there are automated tools and solutions that can make it much easier.  

Intruder continuously scans your network so you can see where you’re vulnerable. It shows you what’s exposed to the internet, and prioritizes issues so you can focus on fixing the most important ones first. Plus, any time it sees a change, such as an emerging threat, new cloud asset or an exposed service, it’ll kick off a new scan for you.  

This means you have visibility and control over your attack surface, you’ll be notified of any changes to your IT environment such as open ports, and automatically synchronize hostnames or IPs. Put it through its paces with a free trial and make your organization as secure and resilient as it can be.

Release Date
Level of Ideal
Before CVE details are published
Limited public information is available about the vulnerability.

Red teamers, security researchers, detection engineers, threat actors have to actively research type of vulnerability, location in vulnerable software and build an associated exploit.

Tenable release checks for 47.43% of the CVEs they cover in this window, and Greenbone release 32.96%.
Day of CVE publish
Vulnerability information is publicly accessible.

Red teamers, security researchers, detection engineers and threat actors now have access to some of the information they were previously having to hunt themselves, speeding up potential exploit creation.

Tenable release checks for 17.12% of the CVEs they cover in this window, and Greenbone release 17.69%.
First week since CVE publish
Vulnerability information has been publicly available for up to 1 week.

The likelihood that exploitation in the wild is going to be happening is steadily increasing.

Tenable release checks for 10.9% of the CVEs they cover in this window, and Greenbone release 20.69%.
Between 1 week and 1 month since CVE publish
Vulnerability information has been publicly available for up to 1 month, and some very clever people have had time to craft an exploit.

We’re starting to lose some of the benefit of rapid, automated vulnerability detection.

Tenable release checks for 9.58% of the CVEs they cover in this window, and Greenbone release 12.43%.
After 1 month since CVE publish
Information has been publicly available for more than 31 days.

Any detection released a month after the details are publicly available is decreasing in value for me.

Tenable release checks for 14.97% of the CVEs they cover over a month after the CVE details have been published, and Greenbone release 16.23%.

With this information in mind, I wanted to check what is the delay for both Tenable and Greenbone to release a detection for their scanners. The following section will focus on vulnerabilities which:

These are the ones where an attacker can point their exploit code at your vulnerable system and gain unauthorised access.

We’ve seen previously that Tenable have remote checks for 643 critical vulnerabilities, and OpenVAS have remote checks for 450 critical vulnerabilities. Tenable release remote checks for critical vulnerabilities within 1 month of the details being made public 58.4% of the time, but Greenbone release their checks within 1 month 76.8% of the time. So, even though OpenVAS has fewer checks for those critical vulnerabilities, you are more likely to get them within 1 month of the details being made public. Let’s break that down further.

In Figure 10 we can see the absolute number of remote checks released on a given day after a CVE for a critical vulnerability has been published. What you can immediately see is that both Tenable and OpenVAS release the majority of their checks on or before the CVE details are made public; Tenable have released checks for 247 CVEs, and OpenVAS have released checks for 144 CVEs. Then since 2010 Tenable have remote released checks for 147 critical CVEs and OpenVAS 79 critical CVEs on the same day as the vulnerability details were published. The number of vulnerabilities then drops off across the first week and drops further after 1 week, as we would hope for in an efficient time-to-release scenario.

Figure 10: Absolute numbers of critical CVEs with a remote check release date from the date a CVE is published

While raw numbers are good, Tenable have a larger number of checks available so it could be unfair to go on raw numbers alone. It’s potentially more important to understand the likelihood that OpenVAS or Tenable will release a check of a vulnerability on any given day after a CVE for a critical vulnerability is released. In Figure 11 we can see that Tenable release 61% their checks on or before the date that a CVE is published, and OpenVAS release a shade under 50% of their checks on or before the day that a CVE is published.

Figure 11: Percentage chance of delay for critical vulnerabilities

So, since 2010 Tenable has more frequently released their checks before or on the same day as the CVE details have been published for critical vulnerabilities. While Tenable is leading at this point, Greenbone’s community feed still gets a considerable percentage of their checks out on or before day 0.

I thought I’d go another step further and try and see if I could identify any trend in each organisations release delay, are they getting better year-on-year or are their releases getting later? In Figure 12 I’ve taken the mean delay for critical vulnerabilities per year and plotted them. The mean as a metric is particularly influenced by outliers in a data set, so I expected some wackiness and limited the mean to only checks released 180 days prior to a CVE being published and 31 days after a CVE being published. These seem to me like reasonable limits, as anything greater than 6 months prior to CVE details being released is potentially a quirk of the check details and anything after a 1-month delay is less important for us.

What can we take away from Figure 12?

Figure 12: Release delay year-on-year (lower is better)

With the larger number of checks, and still being able to release a greater percentage of their remote checks for critical vulnerabilities Tenable could win this category. However, the delay time from 2019 and 2020 going to OpenVAS, and the trend lines being so close, I am going to declare this one a tie. It’s a tie.

The takeaway from this is that both vendors are getting their checks out the majority of the time either before the CVE details are published or on the day the details are published. This is overwhelmingly positive for both scanning solutions. Over time both also appear to be releasing remote checks for critical vulnerabilities more quickly.

Written by

James Harrison

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