128 Internet Blacklists & Home Internet Security: Can Too Much Protection Block the Good?
Part 2 — Understanding Wi-Fi Security, DNS Filtering, Internet Blacklists, and the Risk of Blocking Innocent Websites
Digital Life Security Series ...Practical ways to protect your devices, accounts, privacy, information and home
When Protection Becomes a Barrier
Home internet security has changed dramatically over the years. What once required specialized software and technical knowledge is now often built directly into our Wi-Fi routers.
Many modern home networking systems offer automatic protection against malicious websites, phishing attempts, suspicious downloads, advertising trackers, and other online threats.
These features can be extremely valuable, particularly for households with multiple computers, smartphones, tablets, smart televisions, and other internet-connected devices.
But they raise an important question: Can internet security become so aggressive that it prevents us from accessing perfectly legitimate websites?
In Part 1, we examined internet blacklists, including UCEPROTECT, and how broad network-level listings can affect innocent email servers.
Now let's bring that discussion into our homes and examine what happens when security systems decide which websites we should be allowed to visit.
How Home Internet Security Works
Most home networks connect to the internet through a router. The router allows multiple devices to share an internet connection and provides a basic separation between the home network and the public internet.
Traditional router security includes features such as firewalls, network address translation, and Wi-Fi encryption.
Modern security services can go further by examining requests for websites and other internet services.
For example, when someone attempts to visit a website, a security service may compare the requested domain against information about known phishing sites, malware distribution networks, or other potentially dangerous destinations.
If the destination is considered unsafe, the service may prevent the connection.
Ideally, this happens before malicious content reaches the user's device.
However, the effectiveness of this approach depends heavily on the quality of the information used to make those decisions.
Understanding DNS: The Internet's Address Book
To understand modern home filtering, we first need to understand the Domain Name System, commonly called DNS.
People prefer names such as example.com, while internet connections generally require numerical IP addresses.
DNS helps translate domain names into the addresses computers need to establish connections.
When you enter a website address into your browser, your device typically obtains the corresponding IP address through DNS, often using cached information when available.
Security services can participate in this process.
Instead of returning the requested address, a filtering DNS service may refuse the lookup, return a blocking response, or direct the user toward a warning page.
This approach can prevent access to many known dangerous destinations without requiring separate security software on every device.
However, DNS filtering has limitations. A website may use several domains, a domain may serve both legitimate and unwanted content, and some applications use their own encrypted DNS connections.
DNS filtering also does not necessarily inspect the actual contents of an encrypted website connection.
Not All Blacklists Are Designed for the Same Purpose
This is one of the most important distinctions in our discussion.
An email spam blacklist and a malicious website blacklist are not necessarily interchangeable.
An email blocklist may identify an IP address because it has sent unsolicited email. A web security list may identify a domain because it distributes malware or attempts to steal passwords.
These are different behaviors, and the evidence supporting each classification may be very different.
Consider a legitimate woodworking website hosted on a server operated by a large hosting company.
Somewhere else within that company's network, an unrelated customer may be sending spam.
A broad email blocklist might include the entire network because of that customer's activity.
But does that mean the woodworking website is dangerous to visit?
Not necessarily. The website may be completely legitimate, securely maintained, and entirely unrelated to the spam activity.
A network's email reputation is not the same thing as the security reputation of every website operating within that network.
How Big Is Your Internet Neighborhood?
In Part 1, we asked an interesting question: When a blacklist refers to a problem in your internet neighborhood, how large is that neighborhood?
On the internet, neighborhoods are not defined by streets or houses. They are defined by IP address allocations, routing systems, and the policies of the organizations evaluating them.
A small IPv4 network might contain just 16 addresses. Another might contain 256, 4,096, or 65,536 addresses.
An autonomous system operated by a large internet service provider or hosting company may contain many separate networks and potentially millions of addresses.
UCEPROTECT Level 2 can include larger address allocations, while Level 3 can include an entire autonomous system when its criteria are met.
Imagine being told that your home is considered suspicious because someone elsewhere in your town committed a crime.
Now imagine that the definition of your neighborhood includes not just your street, but thousands of homes across multiple communities.
That illustrates the problem with applying broad network reputation to individual users.
Large network providers do have a responsibility to address abuse. However, an innocent customer may have no knowledge of, or control over, the actions of unrelated customers.
The larger the neighborhood, the more carefully we should interpret what its reputation actually tells us.
What Happens When an Entire Network Is Blacklisted?
In Part 1, we examined UCEPROTECT's three levels of email blocklisting.
Level 1 focuses on individual IP addresses. Level 2 can include larger IP allocations, while Level 3 can include all addresses assigned to an autonomous system, or ASN.
UCEPROTECT acknowledges that its Level 3 policy can produce collateral damage when used for email blocking and recommends incorporating the information into a scoring system rather than automatically rejecting every matching email.
Now imagine a hypothetical home security product that takes this same broad network listing and uses it to block website access.
If an entire hosting network is classified as unacceptable, the filtering product could potentially make large numbers of unrelated, legitimate websites inaccessible.
The website owners might have done absolutely nothing wrong.
This is not evidence that a particular home router currently behaves this way. It illustrates the consequences that could follow from applying an email-oriented network blacklist indiscriminately to web browsing.
How Many Websites Could Be Affected?
This is an intriguing question, but it is more difficult to answer than it first appears.
Millions of websites use shared hosting, cloud platforms, content delivery networks, and other forms of shared infrastructure.
Some websites share a public IP address with many other domains. Others use multiple IP addresses or distribute their content across different networks.
We cannot determine the percentage of websites potentially affected by a particular blacklist simply by counting its listed IP addresses.
We would need to identify which websites actually use those addresses, distinguish active websites from unused addresses, account for content delivery networks, and determine how the security product applies its filtering rules.
Even then, a website might be reachable through multiple network paths.
Nevertheless, broad network blocking could affect a substantial number of legitimate websites under the wrong circumstances.
That possibility alone demonstrates why security systems should use carefully selected threat intelligence rather than indiscriminately combining every available blacklist.
What About eero and Advanced Security?
One popular home networking system is eero, which offers mesh Wi-Fi networking and additional security features through eero Plus.
According to eero's published documentation, its security features include DNS-based filtering intended to help protect users against potentially harmful internet destinations.
Eero also provides features for advertising blocking, content filtering, and manually blocking or allowing specific websites.
These capabilities can be helpful for families and individuals who want network-wide protection without installing separate software on every device.
However, an important question arose during our research: Does eero use every available internet blacklist, including UCEPROTECT Level 2 and Level 3, to determine which websites are accessible?
We found no published evidence establishing that claim.
Eero's documentation confirms DNS-based security filtering, but it does not establish that UCEPROTECT's broad email network listings are used to block ordinary web browsing.
Therefore, it would be inappropriate to claim that eero automatically blocks websites simply because their hosting networks appear on UCEPROTECT.
It is also important to distinguish between the possibility of a filtering system using IP reputation information and evidence that a specific product actually uses a particular list.
When evaluating internet security, we should ask for documentation or reproducible evidence rather than relying on assumptions.
Why Using Every Blacklist May Not Improve Security
At first glance, using more blacklists might seem like a good idea.
If one list identifies dangerous websites, wouldn't ten lists provide ten times the protection?
Unfortunately, security does not work quite that way.
Different lists may use different standards. Some identify confirmed malicious activity, while others classify entire networks based on statistical patterns or indirect associations.
Some lists are updated frequently. Others may contain outdated information or addresses that have been reassigned to new customers.
Combining lists without evaluating their quality can increase false positives, situations where legitimate activity is incorrectly classified as dangerous.
There is also a difference between a warning and an automatic block.
A moderately suspicious destination might justify additional examination, while a confirmed phishing site may warrant immediate blocking.
Responsible security systems should distinguish between these situations.
More blocked addresses do not automatically mean better protection.
The Gmail and Outlook Comparison
Consider an example from email security.
Major email providers such as Gmail and Outlook serve enormous numbers of legitimate users. Unfortunately, criminals can also misuse accounts on these services to distribute phishing messages.
If some users of a major email service send fraudulent messages, should every account associated with that provider be considered suspicious?
Doing so could interfere with countless legitimate communications.
Receiving mail systems therefore benefit from examining individual messages, authentication, sending behavior, and other indicators rather than judging every sender solely by the name of the provider.
The same principle applies to website security.
A hosting provider may have some customers engaged in abusive activity, but that does not establish that every website operating within its network is dangerous.
Network-level reputation can be a useful signal, particularly when a provider has persistent abuse problems. But it should be interpreted in context rather than automatically applied as a verdict against every customer.
The Human Cost of False Positives
Imagine a small business that has spent years developing a trustworthy website.
The owner maintains the software, uses HTTPS, protects customer information, and carefully manages email accounts.
One day, customers begin reporting that the website is inaccessible from certain home networks.
The site works normally from other locations, and there is no indication that it has been compromised.
Eventually, the owner discovers that a security service has incorrectly classified the website or some of its supporting infrastructure.
The business may lose visitors, customer inquiries, and sales while trying to determine what happened.
False positives can also affect nonprofit organizations, educational resources, community websites, and personal projects.
For smaller organizations without dedicated technical staff, diagnosing such problems can be especially difficult.
Security providers therefore have a responsibility to balance protection with accuracy and provide practical ways to investigate and correct mistaken classifications.
What Should You Do When a Website Is Unexpectedly Blocked?
If a website suddenly becomes inaccessible, do not immediately assume that it is dangerous or that your router is responsible.
First, determine whether the problem affects only one device, the entire home network, or visitors using other internet connections.
If the problem appears related to a security filter, consider the following steps:
- Check the website address. Make sure the address is correct and that you are not following a misleading link.
- Read any security warning. Look for the reason the site was blocked, if one is provided.
- Check the router's security settings. Determine whether content filtering, parental controls, or malicious-site protection might be involved.
- Compare carefully with another connection. Testing from a trusted cellular connection may help determine whether the issue is specific to the home network. A site loading elsewhere does not prove it is safe.
- Investigate the domain's reputation. Reputable security services may provide information about why a site has been classified as suspicious.
- Contact the website owner or security provider. A legitimate website may have been classified incorrectly, or it may have a real security issue requiring attention.
- Use exceptions cautiously. If the website has been independently verified as trustworthy, an allowlist may provide a solution. Never bypass a serious security warning simply because a website is familiar.
For eero users, the company documents options for allowing individual domains and temporarily disabling certain filters for troubleshooting.
Temporarily changing a security setting can help isolate a problem, but protection should be restored afterward, and suspicious websites should not be trusted without further investigation.
Security Is More Than Blacklists
Home network protection is most effective when it combines several complementary safeguards.
Strong Wi-Fi encryption, updated router firmware, secure passwords, multifactor authentication, operating system updates, browser protections, and reliable backups all contribute to a safer digital environment.
DNS filtering and reputation services can add another valuable layer, but they should not be considered complete protection against every threat.
For example, a phishing website may be too new to appear on a blocklist. A legitimate website may become compromised after previously maintaining an excellent reputation.
Some attacks also originate from malicious email attachments, compromised applications, or deceptive messages rather than visits to known dangerous domains.
No single blacklist or filtering service can identify every threat accurately.
Good security uses multiple layers and remains adaptable as new information becomes available.
Transparency Matters
As security products increasingly make automatic decisions on behalf of users, transparency becomes more important.
Consumers should be able to understand what types of threats a product attempts to block, how to investigate unexpected restrictions, and how to report suspected mistakes.
Security companies may have legitimate reasons not to publish every detail of their detection systems. Revealing too much information could help attackers evade protection.
Nevertheless, meaningful explanations, review procedures, and reasonable user controls can improve confidence in security products.
When a legitimate website is blocked, users and administrators should have some practical path toward identifying and resolving the problem.
The goal should be accurate protection, not simply maximizing the number of blocked destinations.
Finding the Right Balance
Internet security requires a balance between preventing genuine threats and preserving access to legitimate information.
Too little protection leaves users exposed to phishing, malware, and other harmful activity.
Excessively broad protection can interfere with ordinary browsing, business operations, and access to valuable resources.
The challenge is not choosing between security and accessibility. It is developing systems that provide both whenever reasonably possible.
That requires accurate threat intelligence, sensible policies, timely updates, and recognition that innocent websites sometimes share infrastructure with problematic users.
It also requires understanding that an IP address, a domain name, an email server, and an entire hosting network are not interchangeable security identities.
Final Thoughts: Protecting the Internet Without Closing It
Modern home security systems offer remarkable capabilities. They can help prevent dangerous connections before users even realize a threat exists.
These technologies deserve recognition for the protection they provide.
But automatic security decisions should always be evaluated with an understanding of their limitations.
A server's appearance on a broad email blacklist does not necessarily establish that its websites are dangerous. A hosting provider's reputation does not automatically describe every customer operating within its network.
And combining more blacklists does not guarantee more accurate protection.
As internet users, website owners, and administrators, we should encourage security systems that distinguish real threats from innocent associations.
The best internet security does not simply block more. It identifies threats more accurately, protects users effectively, and avoids unnecessary harm to legitimate websites.
Because the ultimate goal of internet security should be to make the internet safer, not smaller.
Further Reading
Brad Zehr | Zehr.net | brad@zehr.net
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