Use the reverse IP address lookup service to identify other sites on your host. Hosts with poor reputation can affect email delivery, blacklisting of your site, and search engine ranking. Using the reverse IP address lookup you can identify how many sites you are sharing that host with. This is common in cheaper shared hosting providers, where a single web server can hosts thousands of small web sites. To cut costs, the web host provider may oversubscribe, that is, sell more web sites than the server can handle. When purchasing web hosting in a shared hosting environment, the web host provider sells small amounts of resources on a server to a number of web sites. These findings can further inform the investigation and lead to additional information sources. Whether responding to an incident, identifying a botnet C2, or simply tracking down noisy Internet scanning, a reverse IP lookup can identify hostnames associated with an attacking system. Incident Response and Threat Intelligence In the above OSINT discovery chart you can see that a reverse IP lookup is one part of the information discovery process. Simply identifying additional hostnames that are related to the target can further inform the information discovery cycle as the new hostnames may have additional DNS records that can point to new target hosts. Even if no vulnerabilities are present, information disclosure can be used to build the penetration tester's knowledge of the target. Using the Reverse IP Lookup technique, it is possible to identify web sites on the host that may contain vulnerabilities to exploit. Following enumeration, a skilled penetration tester will be able to identify weak spots where vulnerabilities may become opportunities for exploitation. With an understanding of the attack surface, the next step is to enumerate the applications and services in use. When attacking a host, one of the first things you will do is attempt to identify the attack surface of the host. Popular Use Cases for the Reverse IP Lookup Attack Surface Discovery for Blue & Red Teams Bing uses its search index to perform the reverse IP lookup and it can still be used today. Making a query such as one in the example will show results from hosts that are using the ip address that matches the query. The search query is straight forward to use. Of the major search engines, Bing is the only service to offer a search query that resolves hostnames from an IP address.Ī few years ago this was a popular method for finding virtual web hosts from an IP address. There are usually not many reasons to use Bing, however, the Bing reverse IP search is sometimes one. Registered members can get up to 500'000 results from a single query using the web form or 6 million using the API (see below). Search hosts across up to a /24 of public IP addresses.įree users are limited by the number of results. Not only can you use the Reverse IP lookup to find web hosts on a single IP address, the query can also be performed against a CIDR network block. Potentially bypassing the security controls of the target site. If for example, your primary target web site appears to be secure, you may be able to gain access to the underlying operating system by attacking a less secure site on the same server. It is also common in many organizations and can be an excellent way to expand the attack surface during reconnaissance of a web server. This is a common technique in shared hosting environments. The technique known as Reverse IP Lookup is a way to identify hostnames that have DNS (A) records associated with an IP address.Ī web server can be configured to serve multiple virtual hosts from a single IP address.