A web filter is a ubiquitous tool for protecting networks and preventing employees or students from accessing inappropriate content. Shockingly the 2019 Insider Threat Intelligence Report from Dtex found that 95% of enterprises caught their employees actively seeking ways to bypass corporate security protocols.
In this article I will outline the methods that employees use to bypass content filtering policies and provide you with tips to prevent them from happening.
Reducing the amount of admin accounts is a strongly recommended security practice. The proliferation of unnecessary admin privileges increases the likelihood that threat actors could gain access to the network through compromised high-privilege accounts.
From a web filtering perspective giving your users limited privileges prevents them from downloading unwanted bypass applications (e.g. proxies) or making configuration changes that can harm the security of your network.
Your company policy needs to explicitly forbid attempts to bypass security measures. An acceptable use policy (AUP) complements your web filter by providing employees with clear guidelines for using technology in the workplace.
An AUP sets a precedent for corrective action should your users attempt to bypass organizational security controls. Once you discover evidence of such attempts you must address the user(s) responsible in a timely manner to dissuade future avoidance attempts.
Free Sample Template:
Employee Internet Usage Policy
Download this FREE acceptable use policy, customize it,
and distribute it to your employees to set a precedent for the acceptable use of the internet in the workplace.
What’s more important: productivity or security?
Distracting and unproductive websites are often blocked in the workplace. Here’s the thing: if your employees really want to use Facebook at work, they’ll find a way.
If you are using a web filter to prevent distractions, disgruntled users are more incentivized to bypass your web filter than they would if it was used solely for security and decency reasons.
From a network security perspective allowing your users to access social media is a lesser concern than incentivizing them to bypass corporate web filtering policies and potentially visit high-risk websites.
Alternatively you can schedule less restrictive web filtering policies during breaks to allow your employees or students to access distracting content at designated periods.
That’s not all, though…
There’s another reason that your employees or students want to get around your web filter. Sometimes it is simply that they want to gain access to content that they shouldn’t be accessing, but that is not always the case. Your web filter may actually be blocking access to legitimate research.
Your web filtering solution needs to be easy to manage. It should allow you to easily unblock websites that have been wrongfully blacklisted. Being able to effortlessly provide access to blocked websites will reduce the temptation for your users to seek out risky filter avoidance techniques.
DNS-Over-HTTPS (DoH) is a protocol that encrypts DNS queries, making the URL visited undetectable to network-level filters. The intention of DoH is to increase the privacy of users by reducing the data available to ISPs and other providers, however it has inadvertently caused problems in corporate environments that use DNS-based web filters.
The very same encryption that hides DNS traffic from ISPs also hides the details that network-level web filters need to effectively block websites.
Employees and students can use web browsers that support DoH to bypass network-level web filtering policies. Some web browsers such as Firefox enable DoH by default, leading to security concerns in organizations that use web filters to protect their network against phishing attacks.
Proxies are websites and applications that act as a gateway between the user and the internet. Companies often use their own purpose-built proxy servers that act as a firewall and web filter but employees can also use third-party proxies to bypass internal content filtering measures.
There are three key ways that proxies can be used to break through corporate web filters:
Effectively preventing the use of proxies requires a multi-pronged approach. You will need to combine web filtering, user permission restriction, USB access control, and application blocking to address all of the possible methods.
A Virtual Private Network (VPN) creates a private encrypted network between two networks. These tools are often used to provide remote workers with access to software applications hosted on their employer’s network.
A VPN bypasses web filters and tunnels through firewalls by masking the network traffic of the user. This makes it difficult to detect or decipher the websites they are visiting, forcing system administrators to block the VPN connection entirely if they want to prevent it from circumventing their filtering policies.
Smartphones include a feature known as “tethering”, which lets you use your phone’s mobile data to create a private Wi-Fi hotspot. This hotspot can be used to connect another phone, tablet, or computer to the internet.
If you are filtering websites at the network level with a DNS filter or firewall your employees can bypass your web filter by disconnecting their work laptop from your filtered network and connecting to their cell phone’s private Wi-Fi hotspot.
An agent-based web filter that blocks websites at the device level cannot be bypassed using this method. The software agent will cache web filtering policies locally, allowing the last known blacklist to be enforced even when your employees connect to an outside network.
Your users can use services such as PortableApps.com to install portable web browsers on a USB flash drive. This method is more difficult to detect than the other methods as the browsers can be launched directly from the removable media device without the need to visit a website or install a program on their computer.
These USB-based web browsers are configured to route their internet traffic through a proxy address that bypasses the internet filtering policies of your network.
Web filters are excellent tools for preventing employees and students from accessing high-risk and inappropriate websites. Over time tech-savvy users have discovered increasingly complex and creative ways to bypass local security policies.
To protect against this trend, restriction-based policies must be combined with computer monitoring and administrative safeguards. Network administrators can further bolster the integrity of their filtering policies by including the use of agent-based web filters that enforce website blacklists when users are off the main network.