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Reverse IP Lookup
Discover all the domain names and websites that are hosted on a single, shared IP address.
TECHNIQUE:
Passive DNS Analysis
SOURCE:
Historical DNS Logs
LIMITATION:
Depends on visibility
What is Reverse IP Lookup?
Unlike Reverse DNS (which only returns the official hostname of an IP), a Reverse IP lookup uses massive databases of passive DNS logs to list every website that currently or historically pointed its A records to that IP.
How it Works
Security providers constantly index global DNS traffic. This tool searches those massive indexes to find all known "A" records that resolve back to the specified IP.
Key Use Cases
Investigating shared hosting environments (e.g., finding out if your corporate website shares an IP with malicious phishing sites).
Mapping the breadth of a competitor's web operations and parked domains.
Identifying secondary brands hosted on the same server.
Advanced Details
Because it relies on third-party historical DNS indexing rather than querying the live server, results may occasionally include domains that recently moved to another host.
Cybersecurity Pros & Cons
Security Advantages
- Reveals co-hosted malicious domains that share your server's IP, triggering collateral blacklisting of your infrastructure.
- Threat actors often host multiple phishing domains on the same IP — reverse IP lookup maps the entire campaign infrastructure.
- Enables rapid IOC (Indicator of Compromise) expansion — one malicious IP can yield dozens of related threat actor domains.
- Shared hosting risk assessment: identifies if your IP neighbourhood contains spam or malware domains before signing up.
Security Limitations
- Historical DNS data may include domains that have long since moved away, creating false associations with current infrastructure.
- Cloud IPs are ephemeral — a malicious domain may have been on the same IP for just hours before you and it diverged.
- Reverse IP data reveals your domain co-location to attackers, potentially identifying your hosting provider for targeted attacks.
- Passive DNS databases have coverage gaps — not all DNS queries are captured, creating an incomplete picture.
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