We now have (experimental) YARA support inside radare2.
If you are building from the latest git, you just have to install
libyara, no need to recompile anything.
[0x00000000]> yara Yara plugin | add [path] : add yara rules | clear : clear all rules | help : show this help | list : list all rules | scan : scan the current file [0x00000000]>
Since you may not already have some rules, we bundled some defaults ones, for packers and crypto primitives.