The list of hosts can be filtered by a filter string. When the filter is active, only the hosts matching the filter string will be shown. The other hosts are still present in the inventory, but hidden. Using a filter string, you can quickly narrow down a large scan to just the hosts you are interested in. Figure 12.12 shows the host filter in action, finding the two hosts out of nine that match apache.

Figure 12.12. Host filter

The host filter is activated by clicking the “Filter Hosts” button, selecting “Filter Hosts” from the “Tools” menu, or pressing ctrl+L. This will raise the filter bar at the bottom of the screen. Hosts are filtered live as you type. To disable the filter, click “Filter Hosts” or press ctrl+L again to hide the filter bar.

This simplest form of host filtering is basic keyword matching. Enter one or more strings such as apache, linux, or telnet, and it will match hosts that have the string anywhere in their information—as a hostname or IP address, port name or number, OS match, or service version string. If more than one word is in the filter string, all the words must match for a host to be shown.

For more specific results, the host filter also supports matching only specific data fields in each host. The syntax supported is a subset of the search criteria discussed in detail in the section called “Searching Saved Results”. The criteria allowed in the host filter are

Here are some examples of host filter strings.