Regarding the $2016$ U$.$S$.$ presidential election, no evidence of cyberattacks resulting in altered voting tallies has been found. At that time, such tampering by foreign cyber$-$intelligence hackers would have been difficult to execute because:

a$.$ the voting machines themselves had military$-$grade firewalls to repel cyberattacks

b$.$U$.$S$.$ intelligence agencies pre$-$emptively attacked the hackers' networks with Stuxnet

c$.$ the voting machines themselves were not connected to the Internet

d$.$ the hackers had no way to profit from even successful attacks on voting machines

e$.$ white$-$hat hackers employed by local election authorities could foil the cyberattacks