the ATtiny85 is a cheap alternative to the rubber ducky and is a microcontroller that acts as a keyboard to run scripts that are malicious to a user in order to gain a reverse shell,meterpreter or to even send off there saved passwords to the attackers email.
the reason to buy the ATtiny85 is because it could be brought off many stores such as ali express, amazon Alibaba for a cheap amount costing around 3 pound with delivery. Because of it being cheap and handy to buy it is used for an alternative for the infamous rubber ducky. If users do not wish to break the bank and want to achieve the roughly the same goals as the the ruber ducky i will recommend them buying the the ATtiny85 because not only the ATtiny85 could run scripts like the rubber ducky but if you lose the rubber ducky you will need to keep buying the expensive device that costs 80 pound
some downsides that the ATtiny85 has is that when uploading your script to your computer you will need to be mindful of your own script running on your own pc or laptop. This is because when to upload your script on the Arduino IDE the ATtiny85 usually has a time limit on when the script should run usually 5 seconds meaning that if you do not turn it off from the Arduino IDE fast enough the malicious script will run on your own pc and laptop. Another reason why i wouldn't recommend the ATtiny85 is because it could break easily when bending it on the usb port as well as it is not concealed well enough like the rubber ducky as it will look suspicious to a user if he tried to plug it in with someone watching.
when buying the ATtiny85 you will need to look for the best shop online to buy it from if you are on a time constraint you would want to ideally buy it from brands like amazon even though it is more expensive the microcontroller will arrive way faster than the shops from ali express or ali baba. However if you would want it way cheaper and could wait for a bit of time it is better to buy the ATtiny85 from ali express or ali baba this is because from my own experience i have brought it from ali express and although i brought it for 3 pound including delivery i had to wait 2 weeks for the microcontroller to arrive
Ali express (cheap but delivery long)