PTR Equals IP: Optional Blocking for Generic Reverse DNS in BotBlocker

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.

What Does “PTR Equals IP” Mean?

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).

How BotBlocker Checks and Blocks PTR = IP

When this option is enabled, BotBlocker will:

• Perform a PTR lookup for every visitor’s IP address.
• If the result is just the IP in a different format (dashes instead of dots, plain IP, or obvious patterns), the request can be blocked, challenged with a captcha, or logged (depending on the settings).

This filter is not active by default, as it can occasionally block legitimate users from ISPs or mobile providers with generic PTR records.

Why Block Generic PTR Records?

• Many bots and automated attacks come from infrastructure where reverse DNS is left at default or mass-assigned.
• Generic PTRs are a strong risk signal, especially when combined with other anomalies (like empty User-Agent, proxy detection, VPN, Tor etc).
• It allows you to further reduce unwanted traffic, especially if your audience is mainly from regions with well-configured ISPs and hosting.

When This Filter is Useful

• On private, corporate, or local sites where all legitimate users come from trusted providers with custom PTRs.
• For blocking traffic from mass-market VPNs, rotating proxies, and cheap VPS providers.
• When combined with other filters for multi-factor decision making (e.g., only block if PTR is generic and User-Agent is missing).

When to Use With Caution

• On public sites or in countries where ISPs often use generic PTRs for normal users.
• For global projects, where mobile and residential connections might not have custom reverse DNS.
• When user experience is more important than maximum strictness – false positives may impact real visitors.

How to Enable

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.

FAQ

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.