How we identify the 95% of anonymous traffic on our B2B site (and the tech behind it)

We all know the pain: you pour money into content and ads, traffic spikes, but 95% of those visitors bounce without filling out a form. For a B2B SaaS, that’s just money evaporating.
We started looking into Website Visitor Identification (WVI) to fix this. It sounds like black magic, but the tech stack behind it is actually pretty straightforward (and surprisingly compliant if you do it right).
The Tech Behind the Curtain:
It basically works in three steps:
The Digital Handshake: When a user hits your site, you capture their IP address.
Reverse DNS Lookup: You run that IP through a reverse DNS lookup to identify the domain associated with the network. (e.g., an IP resolves to server-5.cisco.com rather than a generic ISP).
The Database Match: You cross-reference that domain against a firmographic database. This tells you "Cisco" is visiting your site, even if the specific employee is anonymous.
Why this matters for Growth: It changes the game from "waiting for leads" to "active hunting." If we see an enterprise company hitting our Pricing and API Integration pages but not signing up, we know they have high intent. We can then trigger an outbound sequence or retarget that specific account on LinkedIn.
It’s effectively de-anonymizing your funnel without violating GDPR (since you are identifying the company, not the individual).
The Deep Dive: I wrote up a full breakdown of how this works, the ethics/GDPR side of it, and how to use intent data to actually close these leads.
Read the full breakdown here: Unlock B2B Leads with Website Visitor Identification
Has anyone here built their own reverse-IP lookup tool, or do you mostly rely on third-party APIs for this? I’m curious if the "build vs buy" math has changed recently.