Many reverse engineering techniques for data structures rely on the knowledge of memory allocation routines. Typically, they interpose on the system's malloc and free functions, and track each chunk of memory thus allocated as a data structure. However, many performance-critical applications implement their own custom memory allocators. Examples include webservers, database management systems, and compilers like gcc and clang. As a result, current binary analysis techniques for tracking data structures fail on such binaries. We present MemBrush, a new tool to detect memory allocation and deallocation functions in stripped binaries with high accuracy. We evaluated the technique on a large number of real world applications that use custom memory allocators. We demonstrate that MemBrush can detect allocators/deallocators with a high accuracy which is 52 out of 59 for allocators, and 29 out of 31 for deallocators in SPECINT 2006. As we show, we can furnish existing reverse engineering tools with detailed information about the memory management API, and as a result perform an analysis of the actual application specific data structures designed by the programmer. Our system uses dynamic analysis and detects memory allocation and deallocation routines by searching for functions that comply with a set of generic characteristics of allocators and deallocators.