Tag Archives: blacklist monitoring

Blacklist Monitoring for Cloud Hosting

Originally Posted on Blacklist Monitoring with RBLTracker.

Since our inception, we’ve helped thousands of companies and individuals, from all around the world, stay on top of day-to-day threats related to their email and websites. Recently, with the addition of our Facebook Threat Exchange monitoring, we’re helping those same customers battle social media related threats.

Some of our earliest customers have been cloud hosting and cloud computing companies- companies that provide the backbone of the Internet as we know it today.

Cloud Hosting Providers

One specific challenge with this type of company, is the sheer number of IP addresses and domains to monitor, and the regular re-use of these IP addresses. The last thing you want, is a brand new customer getting an IP address that is already blacklisted because of something the last owner did.

Another key challenge, is making sure that resources are used “only as needed”. Let’s face it- you don’t want to pay to monitor hosts that aren’t being used- and you shouldn’t have to.

We offer a few key features that makes blacklist monitoring for cloud hosting providers, easier and more affordable.

IP Range Host Type

Normally customers add IP addresses and domains (aka “Hosts”) to the RBLTracker portal individually. If you have 10 to 15 Hosts, this isn’t really a big deal. You can add hosts using our bulk loader, or individually. You can also add Hosts as a range or CIDR block (x.x.x.x/y).

But what if you have thousands of Hosts to monitor? At some point it’s going to become unwieldy to provision, and impossible to manage.

To support this, we built a custom “IP Range” Host type. This lets you add IP addresses as a range or CIDR block, but rather than thousands of IP addresses showing under your account, a single Host entry is shown. Our system will still monitor every single IP address individually– but the full block of IP addresses can be managed as a single entry.


So whether you have a few /24’s or a whole /18- you can easily manage the full IP block with ease.


API Provisioning

Loading all your IP addresses into the system is great, but what if you only want to monitor a sub-set of those hosts? Or if you only want to enable monitoring for hosts that are currently in-use?

Several of our customers have opted to integrate with our web-based API, to provision monitoring on IP addresses as they’re allocated to their customers. That way only active IP addresses are being monitored. This ensures that you’re only paying for monitoring that matters- that will actually impact your business or your customers.

The RBLTracker API is easily integrated into any provisioning or monitoring platform, with just a few simple lines of code:

# wget --post-data="type=rbl&name=Test&host=" -qO- https://rbltrack.com/api/host/add.json?api_token=x

    "status_code": 200,
    "status_message": "Hosts added successfully.",
    "data": [
            "id": "37c46a725dd8adab28d35b9f200c198d",
            "host": "",
            "name": "Test"
    "version": "2.0"

Easily enable monitoring on a Host when it’s allocated to a customer, and then disable it when it’s de-allocated- it’s a simple as that.

Contact Groups

When we identify an issue with any of your Hosts, we’ll immediately notify you via several different notification methods. These contacts can be broken down into custom contact groups, and assigned to Host. The end result, is that you can have a unique contact for every host under your account:


Cloud Hosting companies can optionally send alerts directly to their customers, notifying them about issues with their IP addresses and domains, and alleviating some of the burden from their network operations staff.

We regularly add new features and tools to make managing and provisioning monitoring services, easier and more effective for our customers.

How Do RBLs Affect Me? (Part 3)

sbOriginally posted on RBLTracker

In Part 1 and Part 2 of our series, I talked about what RBLs are, how they work, and how RBLs are used by administrators to control the day-to-day onslaught of SPAM on their email systems. In this article I’m going to talk about how RBLs affect you, your business, and why you should care.

So Why Do I Care?

Getting listed on an RBL or URIBL is not uncommon- it happens.

  • Maybe you have a customer using your email platform that didn’t quite understand the rules against bulk email.
  • Maybe one of your employees downloaded some virus infested software that started sending SPAM to all the contacts in their email client.
  • Maybe your email administrator made a mistake when configuring your email system, and opened you up as an open relay.
  • Maybe the WordPress or Drupal installation on your website was compromised, and injected with phishing code.

We all do our best to ensure that these types of errors aren’t the norm, but human error happens.

As a mail recipient, RBLs protect you from these issues by rejecting these messages before they land in your inbox. As a mail sender, RBLs protect others FROM your issues- and limit your overall liability, by reducing the number of messages delivered.

By listing compromised mail servers and website domains, and using these RBLs and URIBLs in our mail systems, we effectively limit the spread of SPAM and phishing websites, which is good for everybody.

Sounds Great- What’s the Catch?

Once you’re listed- as the name indicates- you’re “black-holed”- much of your email won’t be reaching its destination, and traffic to your websites could be limited.

If your business relies on email communication- either as a tool, or a product- then the longer you’re listed, the worst it is for your bottom line, and your reputation. It looks really bad if your customers email you, and get a bounce message indicating that your email system has been blocked.

The sooner you know there is an issue, the sooner the issue can be resolved, and the sooner you can request delisting from the RBLs in question.


RBLTracker provides a fully automated RBL monitoring service, which checks your IP addresses and website domains, against a customizable list of the top DNSBLs, and will alert you immediately if your system is listed.

Don’t wait days or weeks to find out that your email hasn’t been reaching your customers- click here to find out more!

How Are Blacklists Used? (Part 2)

Originally posted on RBLTracker Blacklist Check Service blog.

In Part 1 of our series we talked about what RBLs are, and the different types of RBLs. In this article, we’ll talk more about how they can be used by administrators to control the flow of SPAM into their networks.

How Are They Used?

Most mail server software can be configured to make requests against DNSBLs, and reject or accept mail, based on if the sending mail servers IP address is listed in the DNSBL. Or in the case of URIBLs, if a domain name or website URL found in the body of the message is listed.


As a quick example, the Exim mail transfer agent (MTA) supports specifying one or more DNSBLs during the ACL processing of an inbound SMTP message.


Exim will make a DNS lookup request on the sending mail servers’ IP address, and if found in the DNSBL, can reject the message with a specific error message.

The Postfix MTA allows administrator to add one or more DNSBLs using the reject_rbl_client configuration option in the smtpd_recipient_restrictions option.


You can also do a simple check on Windows, Mac, and Unix, using the command line nslookup tool. Simply reverse the digits in your IP address, and prefix it to one of the DNSBL host names.

So for example, if your IP address was and you wanted to check the bl.spamcop.net DNSBL, you would do a DNS lookup on:


Check back for Part 3 of our series where I talk about how RBLs affect organizations, and why they can be an important part of your day-to-day administration.

What are Blacklists and How Do They Work? (Part 1)

Originally Posted on RBLTracker Blacklist Check Service

Real-Time Blacklists (RBL) are a simple but effective way for organizations around the world, to share the location (in this case, the IP addresses) of email systems that are reputed to send email SPAM.

The most common implementation of these lists are distributed via DNS, and referred to as DNS-based Blacklists (DNSBL). Distributing this data via DNS makes perfect sense; it’s a technology that already exists, and servers all already have access to. It’s fast, and the data (IP addresses and domains) is well suited for DNS.

Types of RBLs

There are hundreds of RBLs available worldwide, managed by hundreds of organizations and individuals. Most RBLs are free to use, some are pay-to-use, and they all have their own methodologies for compiling their databases, and their own processes for being delisted.

Two of the most common and reliable methodologies for collecting data for RBLs, are based on user input, or something they call a “honey pot”.

Crowd Sourced

RBLs based on user input are the most common, and often most reliable. This data is effectively crowd sourced. When an email recipient receives a SPAM message (assuming their system supports it), they can “flag this message as SPAM”. If enough recipients flag the same message as SPAM, the IP address of the sender will be added to the RBL database.

This is common in free email services like Hotmail and Gmail.

Honey Pots

Another common source for RBL data is something called a honey pot. These are basically email addresses that are never used for any legitimate email purposes, and aren’t owned by any end users. They simply exist out on the Internet in places where robots and SPAM aggregators collect email addresses.

Any email that comes to these addresses is by definition unsolicited, and considered SPAM, and will land you on an RBL.


Another type of RBL is the URI Blacklist (URIBL). This is used for distributing domain names of websites that are reputed to send SPAM or to be involved in phishing schemes. So this doesn’t just affect organizations that run their own mail servers, but anyone that has a website as well.

There are definitely RBLs that are more reputable than others; there are some that have no process for being delisted, and others where you have to pay to be delisted. In my opinion, the pay-to-delist RBLs should not be considered reputable, and should not be used by mail system administrators.

Stay tuned for Part 2 of this series, where I’ll talk about how these RBLs are used by organizations, and give you some real-world examples of how RBLs can help you combat SPAM.