Final answer:
Format string attacks in C or C++ involve misuse of string formatting functions, which can lead to unauthorized memory access. They differ from buffer overflows that overwrite memory due to exceeding buffer limits. Both attacks can be combined for more targeted exploitation.
Step-by-step explanation:
Characteristics of Format String Attacks
A format string attack occurs in C or C++ when a program uses user input as the format string parameter in string formatting functions like printf, without proper validation or sanitization. This vulnerability allows an attacker to read or write to memory by utilizing format specifiers such as %s or %x. The issue arises because the format string can control the number of arguments expected to be processed by the function, leading to unintended memory access.
Difference Between Format String Attacks and Buffer Overflows
Although both format string attacks and buffer overflows are memory corruption vulnerabilities, they are distinct in nature. A buffer overflow occurs when data exceeds a fixed-size buffer, potentially allowing an attacker to overwrite memory, including return addresses and function pointers. In contrast, a format string attack doesn't require exceeding buffer limits; it exploits the string formatting functions themselves. Both can lead to arbitrary code execution, but they leverage different mechanisms.
Combination of Attacks
An attacker could combine both vulnerabilities to escalate the impact. For instance, a buffer overflow could be used to overwrite a pointer to control where a subsequent format string payload would write to or read from, allowing for more precise memory manipulation and potential exploitation.