Types of Attacks

The attacks, including the ones mentioned in Section 3.2.1, can be categorized in several groups by the nature of their functioning [9]:

• Buffer Overflows: a problem endemic to C programs that provide poor bounds checking on input received from outside environment resulting in subverting the intended flow of program and thus forcing execution of attacker supplied code^3.1. Five out of the seven vulnerabilities mentioned in Section 3.2.1 belong to this category.
• Race Conditions: intended functioning of a program can be subverted so that it produces side effects that compromise system security. Some of ``R Commands'' vulnerabilities from Section 3.2.1 fall into this category.
• Special Character Processing: rely on ``fooling'' character processing programs by providing user input that causes the program to relinquish control to the attacker. Programs affected are usually CGI scripts running in privileged mode and accessible by everyone.

As can be seen, by far the most frequent are attacks that are based on the buffer overflow technique.

Footnotes

... code^3.1

In C, both function return address and local variables are kept on stack. By supplying a function argument longer than the local variable it is subsequently copied to, an attacker may overwrite contents of the stack, including the return address. If carefully chosen, the overwritten return address can point to custom supplied piece of code eg. code for executing system shell.