From the Find options in Maltego, you can search your current graph as well as any saved graphs stored on your machine.
Quick Find
The Quick Find option on the Investigate tab is a handy tool to find something specific in a very large graph. The Quick Find toolbar will open at the bottom of your graph. The Quick Find toolbar can also be accessed using Ctrl + F as shown in the image below:
You can now enter a search term, select the specific entity type or specify All (the whole graph) and you have the option to search all the Properties, Notes and Detail View. You can also search text in links.
On clicking the Find button, the relevant Entities will be highlighted in the graph and the search hits will be listed in the Detail View. If the Zoom checkbox is ticked, your graph will zoom to the search results matching your search criteria.
Find in Files
Find in Files does exactly what the title suggests, it allows you to perform text searches on multiple Maltego graphs that are saved in specified folders on your machine.
Clicking the Find in Files button opens the window shown below:
Inside the Where field you can specify the folder that you wish to search. This folder must include .mtgl and/or .mtgx graph files. The Browse button can be used to open a directory window where you can navigate to the folder you wish to search. If the folder that you choose has multiple sub-directories that you also wish to search, then you must check the Recursive checkbox.
The Find input field allows you to specify your search term. The Case Sensitive checkbox can be used to choose whether the search should be case sensitive or not.
The options from the Graph Items field will allow you to choose whether to search Entities and/or Links. It also allows you to limit your search to a specific Entity type from the drop down menu.
Finally, the Search In field allows you to choose which of the Entities' text fields should be searched.