There is no doubt that the RTL-SDR project has made radio hacking more accessible than ever, but so far you can go with a reassigned TV tuner. Obviously, the biggest drawback is the fact that you can only listen to signals, not transmit them. If you’re willing to reach out and touch someone, but you don’t necessarily want to spend the money on something like HackRF, RF Evil Crow RF can be your perfect next step.
This Creative Commons licensed board combines two CC1101 and ESP32 radio transmitters in one convenient package. Radios give you access to frequencies between 300 and 928 MHz (with some gaps), and the fact that there are two of them means that you can listen on one frequency while transmitting to another; opening up interesting opportunities for signal retransmission. With the standard firmware, you connect to a web interface running ESP32 to configure basic receive and transmit options, but there is also a more advanced RFQuack firmware that allows you to control the hardware via Python running on the host computer.
One particularly nice feature is the series of buttons located on the side of the Evil Crow RF. Because the device is compatible with the Arduino IDE, you can easily modify the firmware to set different functions or actions of the buttons.
In a demonstration by a leading developer [Joel Serna], the physical buttons are used to trigger a re-attack while the device is plugged into a standard USB power bank. There is a lot of potential for covert operations, which makes sense since the device is designed with pentesters in mind.
As an open source project, you can create your own version of Evil Crow RF, but those looking for a more key experience can order prefabricated board from AliExpress for $ 27 USD. This approach to hardware production seems to be becoming increasingly popular among the open source crowd, with Open-SmartWatch offering a similar option.
[Thanks to DJ Biohazard for the tip.]