There is only one way to look imports in a binary, using functions
r2.imports(integer, string, string, string) r2.imports(ordinal, bind, type, name)
Each parameter could be string or regex (except the first one). In case any parameter is indiferent for you, can use empty string "", or -1 if you mean the ordinal, for instance:
We can look for binaries with import called "__ctype_toupper_loc", type "function" and Global and doesn't matter ordinal:
r2.imports(-1, "GLOBAL", "FUNC", "__ctype_toupper_loc")
Some Yara rules examples we can generate: If a binary imports function URLDownloadToFile, we can intuit the sample connects to Internet to download something that it stores to disk:
Function CreateProcessA said us the binary probably will create another process. it suggest when we run the program we must look the additional programs lauch:
To end this part, remember there're common Windows functions found in malware and you can build Yara signatures to detect them.