w00w00 on Heap Overflows

Heap/BSS-based overflows are fairly common in applications today; yet, they are rarely reported. Therefore, we felt it was appropriate to present a "heap overflow" tutorial. The biggest critics of this article will probably be those who argue heap overflows have been around for a while. Of course they have, but that doesn't negate the need for such material.

In this article, we will refer to "overflows involving the stack" as "stack-based overflows" ("stack overflow" is misleading) and "overflows involving the heap" as "heap-based overflows".
http://doc.bughunter.net/buffer-overflow/w00w00-heap.html