Code caves are unused sections of a program's executable code that can be used to redirect program execution to another location. Code caves allow a program to be backdoored by inserting malicious code into the unused sections and using entry instructions like calls or jumps to redirect execution to the malicious code. The code can then return back to the original program location. Several sources are listed that provide information on using code caves to backdoor programs by inserting undetectable malicious payloads.