BotBlocker includes an optional feature to block visitors whose PTR (reverse DNS) records are simply a literal copy of their IP address. This is a sign of non-configured or default server setups, often seen in suspicious or low-trust traffic.
A PTR record that just repeats the IP address (e.g. 12-34-56-78.somehost.com or even just 12.34.56.78) is usually a placeholder, not a real hostname. This indicates that the server owner hasn’t set up reverse DNS properly or that the IP comes from dynamically allocated or mass-market ranges (like cheap hosting, VPNs, residential proxies).
In a well-configured network, every server or service has a proper hostname assigned in reverse DNS. When a PTR lookup returns something that looks like a reformatted IP, it means no one bothered to set it up. This is common with bulk IP allocations used by bot operators, scrapers, and traffic resellers. For site owners, this pattern is one of the cleaner signals to filter out unwanted automated requests without relying on behavioral analysis alone.
When this option is enabled, BotBlocker will:
The lookup itself happens on the server side and does not add visible delay for the end user. BotBlocker compares the resolved PTR value against known patterns: numeric-only hostnames, dotted or dashed IP formats, and other variations that are clearly machine-generated rather than administratively assigned. If a match is found, the configured action is triggered immediately.
This filter is not active by default, as it can occasionally block legitimate users from ISPs or mobile providers with generic PTR records.
According to Cloudflare’s DNS documentation, PTR records are primarily used for reverse DNS lookups and email server validation. The absence of a meaningful PTR value is widely treated as a trust indicator in anti-abuse systems. When a PTR record is just a reformatted version of the IP, it tells you that the IP block was provisioned at scale with no individual configuration, which is a pattern typical of bot infrastructure and low-quality hosting.
This filter works particularly well for e-commerce sites, membership platforms, and any project where traffic quality directly affects revenue. If your ad spend or conversion tracking is being distorted by bot visits, enabling PTR-based filtering is a practical step to clean up the data. It targets a specific, well-defined technical pattern rather than guessing at intent, which makes it reliable when applied to the right audience.
For example, some regional ISPs in Eastern Europe, Southeast Asia, and Latin America assign generic PTR values to residential connections as standard practice. In those cases, blocking every visitor with a generic PTR would filter out real customers. The recommended approach is to start with logging mode, review the data for a few days, and only switch to blocking once you have a clear picture of the traffic patterns on your specific site. You can also cross-reference with Spamhaus DNSBL guidelines to understand how similar signals are used in email filtering, which follows the same logic.
This option is found in the advanced BotBlocker settings panel. Turn it on if you want this extra layer of scrutiny, and monitor the logs to ensure it’s not blocking legitimate users.
Will this block all traffic without custom PTR records?
No, only those where PTR is literally a version of the IP – e.g. 1-2-3-4.isp.net or just the IP itself.
Is this filter enabled by default?
No, it is optional and off by default.
How to reduce false positives?
Use in combination with other checks, or set it to only log suspicious requests at first.
Does this affect site speed?
No. The PTR lookup runs server-side before the page is served and does not affect load time for the visitor.
Can I whitelist specific IPs or ranges?
Yes. BotBlocker allows you to add IP addresses or CIDR ranges to a whitelist, so trusted traffic is never affected by PTR-based rules even if the reverse DNS looks generic.
